Link to latest version of Scope.exe            

ALIGNMENT:       Alt-Az:  Initialization          Equatorial:  Polar Alignment  

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ALTITUDE OFFSET:  

You should use the altitude offset when you are uncertain of your starting altitude (you no longer have to level your tube, for instance).  Do not use it if you are certain of your altitude.        Mel Bartels

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2)  To understand the altitude offset, you should understand the azimuth offset first. Take's coordinate conversion routine only needs the difference in azimuth between positions, not the absolute azimuth position. So, an azimuth offset can be calculated based on the arbitrary starting point where azimuth is set to zero. That is, after completing the coordinate conversion initializations, the true azimuth can be determined of the starting point. This value is the azimuth offset.       Mel Bartels

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Q.  On my Alt/Az scope, when I do inits, I often forget to do an Altitude Offset. This results in good tracking, but terrible goto's. Since I believe its the same bit of code for both Alt/Az and EQ mounts, does this mean if you have an EQ mount, and you do an Init 1 & 2, that you will need to do an Altitiude Offset as well    James Lerch

A.  Less necessary for equatorial mounts as the simple 'reset to equat' usually guarantees accurate altitude, ie, declination... Mel Bartels

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But that's not necessarily what best for 2 most accurate inits overall.  Calculation and accurate altitude offset does not necessarily show up in the latitude measurement. Do not make a tight coupling between these two.  Altitude and latitude are two different beasts. The 2 star init may reach an apparent accurate latitude but then show a large altitude offset error.  That means that the scope will point accurately in some parts of the sky but not in others. For most accurate results, the altitude offset should be very close to zero and the latitude error should be very close to zero.

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I do an alt-offset after all is supposed to be wonderful, just to verify the inits. The 'test' offset should be very close to zero    Mel Bartels

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The altitude offset is typically done once each evening, as soon as the two stars are initialized. It is best to use two stars at about the same altitude with widely differing azimuths.               Mel Bartels

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(The) Optimum conditions for determining altitude offset not necessarily optimum for overall initialization accuracy!    Mel Bartels

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The declination in a perfectly aligned equatorial will equal the altitude reading.      Mel Bartels

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You can look for optical vs mechanical mis-alignments by running a series of 2 star inits, and after each init 1 and init 2, do the 'a' altitude offset option. Do NOT adjust the offset - just jot down the value. If the value is fairly consistent as you re-do both inits, then this tells you that you like optical:mechanical misalignment. The alt-offset will fix one direction of this. The other is more complicated. If you see consistent alt-offset values, then post back to scope drive list and we can talk more about the perpendicular component.   Mel Bartels

ANALYSIS FILE:

Analysis would help of course, but make sure you solved all random, mechanical (imbalance) and backlash errors in the system first. Otherwise you will basically analyze random errors of the system. Your flexible rubber shaft couplings would be one source of random error for example. Also make sure your scope is collimated accurately before attempting analysis. That is one important source of pointing errors that is often overlooked.   Berthold  Hamburger

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There is a handpad mode called analysis. After the object is centered, push the mode button momentarily to record the position. What gets recorded in the analysis.dat file is the actual altitude and azimuth along with the object's equatorial coordinates, and the sidereal time. These values are later used to construct an error graph, which is essentially the difference between the recorded alt-az and what the alt-az really should have been. This will work regardless of mount type, but the type and degree of error will likely be different.

Z1 and Z2 and Z3 will continue to function regardless of mount type. All mount types will have alt or dec, and az or ra, offsets, and will have axis misalignment.

If you do have an equat and you are not precisely polar aligned, it will show as a relatively smooth sinusoidal curve on the error plots. This can now be fairly compensated for by the new pointing model corrections (PMC), which is under active development to say the least!  Mel 136

To create a series of analysis points. Put the handpad in analysis mode, goto an object from a data file, then precisely center the object using crosshair eyepiece. Record the analysis point by using the handpad's left or right button mode keys. This records the target position, and the error from that target position. Now, pull up the Z1Z2 analysis via menu option. You can play with different values to minimize the rms error. Try to stay on one side of the meridian flip - don't add analysis points from the other side - to do so is not sufficiently tested.

Since you will likely be doing the analysis multiple times, you can build a scroll file to move to an object, record the analysis point, and move on. See the webpages on the handpad and scroll files for details. Mel Bartels 10139

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Remember you can analyze for Z1 Z2 Z3 errors by doing 3 inits and also by doing the analysis file.  Mel Bartels

AUTOGUIDING:                       http://www.bbastrodesigns.com/autoguide.html 

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I did a setup assembling that works great both, for stepper system as well as for Scope II. The idea is not to be dependent on a specific 
camera or with a specific mount electronics but to be based on a standard protocol. The way to do that is to use LX200 based commands for 
autoguiding and a ASCOM driver. Take a look on the following web (http://www.technoplus.nl/astro/lx200.htm). Albert Van Duin is selling a 
LX200 emulator that connects it to a computer, accepting LX200 commands and driving four relays.  
My setup is as follows: The autoguider is based on a Philips TouCamII modified for long exposure and a monochrome CCD sensor. I'm currenly 
usign GuideDog, but it is also possible to use MaximDL, K3CCDTools, ......I have installed an ASCOM driver and I tell to the software that I 
have a generic LX200 telescope. The computer is linked to the LX200 emulator with a serial cable and the LX200 emulator relays are linked to 
the ScopeII handpad buttons.  Roger Artigas

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....use a 6 pin modular Y connector in the handpad plug on the circuit board to provide two handpad ports. Be careful, you want a connector that is wired straight through. The type for normal telephone use crosses pins and will give you nothing but grief. Get one labled for "network or data" use. They are available from Jameco www.jameco.com  for less than a dollar, though they may have a minimum order. Marty Niemi

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For autoguiding, the system must be moded to “Guide+Stay” mode BEFORE the autoguider commands start being sent.  HAS

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Q.  autoguide-software which is directly compatible with scope.exe. Does anything exists? Is it free?

A.  try free guider.exe (if you have a b&w quickcam and a cheapo DOS laptop), and see:

http://www.ghg.net/cshaw/quickcam.htm        http://www.ameritech.net/users/mniemi000/auto.html               Paul Shankland  

A. I too have tried using all of the programs you mentioned (K3CCD Tools, GuideDog, Startrack) but found they all connected ok to scope but motors didn't move.  I gave that up a year ago and tried Guider by Marty Niemi, this worked (made for a B&W webcam) but wasn't compatible with the way I wanted my computers setup, so I went for AstroArt which works fine. 

A  i'm using http://www.technoplus.nl/astro/lx200.htm       It does really great job !   I have my best results with this autoguider in paarallel with the button on the handpad.   i have sometimes problem with autoguiding software crashing with the RS232 commands, but never with this emulator.     Vincent  Steinmetz

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You will need to build the autoguider interface, which is documented in the Cookbook manual. I have an updated version of the circuit I can send you to properly interface it to Mel's circuit. Basically it just looks like another handpadle to Mel's circuit.  

I will be writing up a presentation for the Image-The-Sky conference in Oregon later this year , and will also have it on my website, to capture the details of how I do this. However, the essentials are that I use guide+save mode, and once in mode, I put the autoguider into autotrack mode. When the mode ends I immediately kick the autoguider out of guiding since scope.exe will be in ms mode at that point. The you simply use the menu driven capabilities in the EC menu to extract the PEC data from the guide files into preliminary pec files that another menu command can average together to build a new PEC.dat file. Sounds more complicated than it is......

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Q.   is anyone using Guider.exe with a Philips ToUcam?

A. Guider was written using low level hardware control commands for only one camera, the old B&W Connectix Quickcam.  I would try using some of the autoguider programs such as "guidedog" that use the video for Windows interface to talk to the camera.  I believe that would work with your ToUcam.
Marty Niemi

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A.  The STV is easy to connect as it uses it's own internal relays like the ST-4. There is a schematic in the files, circuits area the shows how to hook up a ST-7,8,.... You do not have to go to the trouble of using that circuit which has it's own relays. The easy way to connect the STV is to use a 6 pin modular Y connector in the handpad plug on the circuit board to provide two handpad ports. Be careful, you want a connector that is wired straight through. The type for normal telephone use crosses pins and will give you nothing but grief. Get one labled for "network or data" use. They are available from Jameco www.jameco.com  for less than a dollar, though they may have a minimum order.

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A.  Put handpad in guide mode, then initiate guiding by pressing the left mode key. Adjust guiding speed as necessary via menu option or config.dat file.  The reason for the additional left mode key press is convenience at the eyepiece. You can turn on/off actual guiding by using the left/right mode keys while the handpad stays in guide mode. This means that the 4 direction buttons toggle from coarse centering when in altaz mode (guide=off) to guiding control (guide=on) depending on your use of the left/right mode buttons. I find this a real convenience at the eyepiece.   Mel Bartels

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A.   I have used Marty Niemi's Guider.exe with the stepper version of scope.exe for years, and it has worked REALLY well for me. I never used the LX200 interface. I always used the hardline interface (i.e. it looks like a 2nd handpad to the PCB). 

Do not use backlash when autoguiding. In theory it should work fine, but in practice its hard to get it to not over correct. You don't need it in RA anyway... And in Dec, if your Polar alignment is not perfect you should be getting a tiny dec drift so you should not need it there either. You want to run the calibration routine twice. The first time backlash in the system may fool it, but the second time it will work well. 

After your calibrations, get the guiding window as small as possible to allow faster downloads. Do not use a star that saturates the detector. If the star is bright, use a short integration and use the averaging routine to average several shots. For bright guidestars I usually shoot at 0.5 sec integrations, and average 3-4, and have the trigger set at one less than the number of images I am averaging to allow a little "persistance"..... 

Most poor guiding is due to chasing the seeing. In poor seeing use a dimmer star to allow a longer integration if at all possible. The longer integration smoothes out the seeing a lot. Once you run the calibration, start messing with the aggressiveness, dialing it down till you are not getting commands that bounce back and forth. I usually have the aggressiveness set at about -3 or so..... Lots of tiny short corrections... but let your mount tell you how often you need to send a guiding correction.... An old rule of thumb is to send a guiding correction no more often than about every 1/10th of the integration time your mount can image unguided. If you can shoot 30 sec unguided, then don't send corrections more often than every 3 to 4 seconds. That allows long integrations and no seeing chasing. If all you can go is 15 sec unguided, then 1.5 to 2 sec. Rules of thumb are just that however.... You have to let your mount tell you how often it needs correcting, but 90% of guiding errors are over controlling (i.e. aggressiveness is too high) or chasing the seeing. The fix is lower aggressiveness and longer guiding integrations.

AXES:

equatorial telescope: altitude is same as declination, azimuth same as hour angle (degrees east/west of meridian however, when you do the gem meridian flip declination is now mapped to altitude so that 

dec = 90 = alt = 90 
dec = 45 = alt = 135
dec = 0 = alt = 180
dec =-45 = alt = 225
notice how dec now travels in reverse compared to altitude and azimuth is mapped to hour angle with displacement of 180 deg

BACKLASH:       http://www.bbastrodesigns.com/operate_backlash.html

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You can adjust the backlash by using the submenu in the control section.

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negative backlash. This unusual option means that the motor will move in the opposite direction than expected in order to take up backlash

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Q.  ...the backlash correction with small movements seems to occur AFTER the button is released.  I would have expected to have occurred when the button was first pressed. Is this normal?

A.  Backlash takes up after the movement.   Rich Bowden

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AbacklashSignalPPortPin17: if non-zero, then parallel port pin 17 used to signal the direction of the 'A' motor backlash: logical high if backlash direction is CCW, logical low if backlash direction is CW (can be used to control motorized counterweights); starting value is logical low.     Mel Bartels

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BALANCE:

Lots of things can change the evenness of the (micro) steps, such as increasing the torque load by unbalancing the tube assembly.             Mel Bartels

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I use a turnbuckle between a pin that is on the exact altitude axis and another one down on the side of the rocker box. You can clamp down a very high pressure then, and eliminate virtually all slippage.... You want to have the OTA balanced as well as possible also.....even though I found I can be pretty far off in balance if I have enough tension set up with the turnbuckles.  Chuck Shaw

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BROWSER:

Microsoft's Internet Explorer:  To make this Web page available offline:

1.   In the Favorites menu, click "Add to Favorites".  2.  Select "Make available offline".

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COLD WEATHER:

If you decide to add a heater, try using a dual-element, 12V tail light bulb with the elements wired in parallel circuit.  Make a clamp o hold the bulb and socket against a robust part of the gearbox case away from the shaft ends.  Use thermal grease between the bulb and gearbox to increase thermal transfer.  Add a thermistor or other Thermometer (a cheap indoor/outdoor or candy thermometer works well).  Then, wrap the gearbox in insulation and seal out the light with Aluminum tape.  Connect the bulb circuit to 12 V supply with a rheostat (dimmer switch or large variable resistor) in series with the + lead. 

 This heater should be capable of producing up to 30 watts of heat, it is reliable & redundant (i.e. if one element blows while observing, the second should be able to keep you going until you can change the bulb) and simple to build.  The drawback is that depending on the temp and your insulation, it could draw a couple of amps. Larry Bell

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Local observatory uses low temperature lithium grease in bearing and gear assemblies.  Mel Bartels

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I use fishing reel lubricant (its a very lightweight grease) that has Teflon in it.  I get it at sporting goods stores.  It does not seem to get stiff in the cold, but it DOES attract dirt. (WD-40 will also wash it out of the gear quite easily when you need to clean things....   

You DO need some type of lubricant.......  I have never found silicone spray to be enough of a lubricant....  WD-40 is NOT a lubricant, it is a solvent and a water displacement material (thats what the WD stands for actually....its the 40th version of a mix of stuff initially used to coat Atlas rocket's outer aluminum skins to protect them from corrosion)  Chuck Shaw

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I too use a 486SX-25 CPU in my old Compaq LTE-Lite4/25c.  I do notice a slight dimming of the LCD screen when I allow it to become cold, but I keep a small cover over the laptop when not looking at the screen, and that seems to help.  Chuck Shaw

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I put the laptop into a box, more precisely a solid plastic laundry basket that is on edge.  The laptop generates enough heat to keep itself warm.  In the observatory on nights down to 0 to -20F, heating blankets might be necessary. Mel Bartels

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I have a couple of 486 laptops that I have used down in the 20s (Fahrenheit) with good results.  They do have active matrix screens rather than the dual-scan variety.  I find that they generate enough heat on their own if you take some measures the retain the heat.  I generally sit the laptop on a piece of closed-cell foam and sometimes lay a towel over the top when I don't need to see the screen.  Normally, I let the hard disk timeout when I first set things up, then turn off the power saving functions and run strictly off floppies.   The floppy seems to tolerate the cold well.  Dan Wilder 

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I use an old 486 for my autoguider and the screen would get slow in the cold. I also found that the screen intensity was too bright in all settings.  So I taped a red transparent plastic in front of the screen ( 1/8" air gap).  It solved both problems !

You could also insulate the back of the screen (glue some thick felt ?). But I haven't had the need  to go that far.  Juan Herrero

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ASCOM:

There are two groups: Ascom-Talk http://groups.yahoo.com/group/ASCOM-Talk  and Ascom-users http://groups.yahoo.com/group/ASCOM-users/   Chris Rowland

Another advantage is that the author does not need to maintain his own extensive set of commands for multiple scopes. All he needs to do is connect to the ASCOM chooser dialogues to let his user pick his scope type.  From that point forward he is assured of a consistant set of commands to control the scope. Gotta ease the work load, I'd think.  Marty Niemi

COMETS - ASTEROIDS - SATELITES:

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Mel and I have a develop a new feature for Scope. It soon will be release. This new feature is the ability to track a comet.  I have created a  program calculates the position of the current comets. Its outputs are a regular DAT file and a CDF file. The CDF file is a new data file format. It contains not only the position of a comet but it also has its drift rates. This allows you track a comet.  Both programs can be download from my website. http://www.geocities.com/kindellism/  Rex Kindell

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A.  Use the menu option to set drift to zero.  Mel Bartels

TRACKING 2002NY40

I want to use the offset equat command in a scroll file to track the asteroid tonight. I've plotted it's position for each hour from 20:00 EDT to 02:00 EDT. I intend to find the target and center it then start the scroll file in auto scroll mode with an offset equat command determined for the positions for each hour (3600 seconds). 

I used The Sky to compute the coordinates based on the location where I'll be observing. I did it for the start of each hour after I downloaded fresh predictions this afternoon.

Do I need to use a minus sign for the RaMin and RaSec since the asteroid will be heading westerly? The DEC is increasing so no problems with the direction of movement.   Don D'Egidio

I am approaching it slightly differently. I built up a .dat file of the RA/Dec data I got from the MPC (5 minute intervals). I also included Vega and Beta Lyra and M57 in the data file to be able to do an offset slew for best accuracy (although I did a 15 deg slew right to it last night).  I took a lot of shots last night where I had NY40 starting at the lower left of the frame, and progress up to the upper right. I was takling 15 sec images each 30 seconds. The result was a series of images of the same starfield but with NY40 in a different spot on each one. I will build a movie from them (I hope). It took 40 images to have NY40 go diagonally across my 10x13 arcmin FOV last night. Since it will be moving about 4 arcmin/min tonight , I will probably only fit in 5 or 6 frames before it is out of the FOV..... Be sure and use topocentric coordinates for the RA/Dec you use tonight since the object is so close. Your location on earth will make a noticable difference in where it appears in the sky, and can throw you off if you are only looking thru a ccd camera's FOV.   Chuck Shaw

I used a completely different approach:
I was using "Guide+Stay" for about 20 minutes tracking with an ST6 on the asteroid itself. Handpadupdate "ON". When the adjustments were within the seeing I stored the values. The drift values became about - 80 in DE and -100 in RA at begin of the night and -180 / -250 at the end. Then I took 80 each 15 sec. exposures (one hour). With this operation the asteroid was almost an hour stable on the pixel.  Because of it's acceleration the drift values had to be updated from time to time (still in guide+stay mode). A .mov file out of that operation has been uploaded (2002 NY40.mov).  Was a great experience with scope.exe.  Thank's Mel. No commercial product allows that.  Rolf

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CIRCUIT:      circuit boards          the stepper circuit            Getting the stepper windings properly hooked up

pcb1.gif  -  Mel Bartels' drawing of his circuit board                   Stepper circuit parts list  (bottom of page)  

Mikel Berrocal and Carmello Fernandez   Board modification for bipolar motors

...the software expects the winding sequence to be A B A- B-, not the A A- B B- that some other controllers ask for.   ...diagram contributed by Bob Rubendunst           Chris Rowland

Mel's answer to current control is Pulse Width Modulation during Microstepping. By Rapidly turning the coil on/off with varied amount of 'on' cycles vs 'off' cycles, the current can be controlled very accurately.  Currently his software can support up to 40 microsteps using this method.  For things like Field De-rotation and Focus control, Mel did rely on independent IC driver's      James Lerch

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The 25 pin "D" connector is what links the board to the computer that provides all the intelligent control. A printer cable connects the 25 pin D connector to the parallel port on the computer (where you would normally plug in the printer). Most people use an old laptop because it's portable, but there's no reason you can't use a desktop PC if you don't need the portability. Most old, cheap computers work well - a 50 MHz 486 DX2 based computer (or anything newer and faster) will work fine. The board simply serves as an interface from the computer, converting the low voltage, low current control signals from the parallel port to the high power signals feeding the stepper motors and providing interface from the handpad to the computer. The small 9 pin "D" connectors go to the motors on the two drive axes. The RJ45 connector (the one that looks like a large phone jack) goes to the handpad. The red and black wires go to your power supply (red to positive, black to negative). The "standard" supply voltage is 12V, although many people (me included) use higher voltages to get better slew speed. I would recommend you start with 12V, that may work fine for you; alot depends on the motors you use. Steve Rivet

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The PCB can support 2-3 amps per winding. If more than that, then use the current limiting circuit to limit current to this level.   Mel Bartels

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I have found that there is approx. 5 volt difference between the controller ground and the laptop frame ground. As soon as I inter-connected the two grounds, the problem stopped. No wonder the motors were rattling as the transistors would have been permanently switched on, so they would have energized all the fields at same time.  Just goes to show that not all laptop power - ground designs allow a "true" ground.   Steve Ross

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a single transformer used to generate two isolated voltages is fine - but be very cautious as the grounds and the supply voltages cannot touch each other! You can also consider those DC to DC converters - use a single voltage source from the transformer, and use a DC to DC converter to step down the voltage and operate the driver board.

The issue of tying the grounds together is like this in my thinking: a common ground is usually OK, as it is unlikely that a voltage spike will travel through the ground into the PC or laptop, and it is unlikely that noise will be a problem on the ground. However, it is possible for voltage spikes and noise to be transmitted on the ground, thus some advocate the totally isolated grounds. In my thinking, in tinkering with circuits for 35 years, it is more likely that you will mess things up by having isolated grounds and forgetting this and accidentally touching something between the two grounds, than it is that a voltage spike or other problems will occur along a single common ground.

In other words, nothing is impervious to destruction, as a virtual shelf full of blown transistors and other components bear silent testimony to at my home!!!    Mel

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..... check your board grounds to ensure the computer ground and 7805 grounds are either properly isolated (if you chose to go that route) or tied together (simplest approach)  Larry Bell

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Make sure you have a solid ground (power return) line to the supplies, Mel's circuit board and the motors. DON'T daisy chain your ground wires. A single point ground with beefy wires will be less prone to ground loops and switching noise.    Larry Bell

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With the same concerns about my laptop's parallel port, here's how I tested my board. Starting with the driver board powered on and disconnected from the laptop, motors and handpad connected:

The 1W zeners can handle 30mA continuous at 30V.  As the voltage drops, the current can increase (P=V*I) and still stay within the power spec.  If you're running your motors at 12V like many people,

the 1W zener will take 80mA continuously.  The 5W zeners can handle 5 times as much, so about 400mA. 

The since the zener is used in a pulsed circuit, the current flowing is not continuous, so you can probably increase the current you put through it without hurting the device.  Its a difficult calculation to determine the peak current flowing in the circuit as the field collapses--I used to be able to do these calcs, but wouldn't want to try it today.  I'd say that if the zener isn't getting hot during a heavy period of slewing or tracking then the 1W is adequate and you shouldn't worry about it.    Larry Bell

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Use the parallel port test function and measure the results at the Collectors of the output transistors.  Select the "H" key and all the Base inputs should go HIGH causing ALL of the transistors to conduct and making ALL of the Collector voltages go LOW. (a voltage around 1 volt is EXPECTED). Make these measurements fairly quickly as the transistors will be ON HARD for the duration of the "H" test and may overheat if left in the ON HARD state (Collectors LOW) for very long

Select the "L" key and all the Base inputs should go LOW causing ALL of the transistors to NOT conduct and making ALL of the Collector voltages go HIGH. (a voltage very close to the power supply input). You can leave the transistors in this state forever without worry.  If this is not the case, then the problem is in the portion of the circuit that is different from the rest. (All 8 channels are identical). You may find that the behavior is exactly the opposite as regarding the "H" and "L" due to circuit differences BUT ...

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board connections: There should be no connections to the three connectors nearest the DB25 connector on Mel's board.  That is for use if you are taking a 5 volt supply from the computer for powering the logic on the board.  The supply voltage to the motors connects to the connector furthest away from the DB25.  The 7805 voltage regulator will supply the 5 VDC for the logic and the signals to the parallel port mn  

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...accidentally hooked up the power backwards. To my surprise, the 47uf electrolytic capacitor exploded. Luckily for me the board was upside down.

Anyway, I was intrigued and sent off for a supply of them. When they arrived, I opened up one end of a small cardboard box and poked the  capacitor wires out through the closed end. 10 out of 10 exploded when 12volts reverse parity power was applied. I bounced the aluminum cans off the ceiling. I shot them along the floor. The greatest distance I managed was 23 feet.

All this surprised the hell out of me, so I thought I would pass the results along and put in a plug for Bob Norgard's protection circuit.  http://groups.yahoo.com/group/scope-drive/files/circuits/Protection_ckt.jpg    bd 9573

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Regarding the circuit protection discussion; there seems to be two camps of folks.  The first puts a fuse in line with the motor power supply circuit (usually the positive lead), then connects a beefy doide between the positive and negative leads in the reversed bias direction so that when power is connected properly, no current flows through the diode.  If the leads are inadvertently connected backwards (i.e. positive to negative and negative to positive as could happen if you're using alligator clips on a car battery), massive amounts of current flow through the diode and the fuse blows open; thus "protecting" the circuits.  This kind'a works, but until the fuse opens, the circuits are subjected to the reverse voltage.  This is  because fuses blow "slow"--even a few milliseconds can do serious damage.  Further, since the circuit can't be easily tested (you must hook up the power backwards to test it) you're never really sure how well protected you are until its too late.  Such a circuit is often referred to as a crowbar circuit.

SECOND CAMP: As several folks pointed out, a better protection method is to simply put the diode in "series" with the positive lead such that current flows when the leads are properly connected.  Of course, in this configuration no fuse is required because the diode prevents any reverse voltage from getting to the circuit if the wires are connected backwards.  This method will result in a very slight voltage drop at the source (between 0.3 and 0.6 volts depending on the diode used).  In most applications this is insignificant.  For those who absolutely must have the full voltage, a better way to protect the circuit is to key the connectors using a harness/connector arrangement that mechanically protects against connecting the positive/negative leads backwards.    Larry Bell

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The scope.exe program has provision for auxiliary control. These are two control lines for you to  use to operate an external motor. For instance, you might operate a dome motor via two solid state  relays that take 5 VDC TTL input       Mel Bartels

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I am building a dual axis, 4 speed, quartz controlled driver for 2 steppers, it is so simple that it requires no laptop nor PC, and no microcontroller at all.  Basically, it is an oscillator, two 74HC4060 divider-counters, and the sequence of both stepping motors is stored in a single EPROM. From it, 4 bits of data output drive one stepper, and the other 4 bits drive the other stepper, by using one 2803 darlington array.

It is as simple as 4 IC, one oscilator, and a remote. As the Eprom can store a lot of info for almost $3, I will store on it 4 speed: tracking, X2 and X8 corrections, and a X128 high speed for rewind my unusual tracking gear system. The tracking speed is achieved by microstepping (4 microsteps per step).

If anybody wants the schematics, I am drawing them in ORCAD, so I can send it, or convert it as an image in a fews more days.  Also I will prepare a hex file with the contents for the EPROM, so anybody could record one As we cannot attach files here, please send me an email to ariel.desseno@m...  (you have to send this through the Yahoo scope-drive group)      Ariel Dessino    4122

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Q.  ...one thing I've found confusing - the diodes for the handpad. No rating/type are specified, can someone provide me with a type/rating for diodes that would work for the handpad? There's a bewildering assortment.

A.  Just about any generic diode will work. I use the 1N4001 from radio shack. 1N914 also works -- just pick a standard rectifing diode.  Current ratings between 0.5 and 1 amp are readily available and are overkill for the application.  Larry Bell

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My controller and all the circuit diagrams that I've seen are meant to be powered indefinitely. That is, the motors can remain powered up for as long as you wish. I've left mine powered for up to 3 days at a time at large star parties so that I can find objects in the daytime based on my nighttime initialization efforts.  

The key is that the software remain in active control of the parallel port.  The parallel port serves as input into the controller. If you have high amperage motors and something else other than scope.exe activates a parallel port control line, it is possible for the motor and possible for the controller to suffer damage from the sustained current flow. This never happens when scope.exe is in control as the software never allows full current  to flow for more than a fraction of a second.  

Some notes on putting the kit together and testing it. Hopefully this will be helpful to others.  \

I unpacked the kit and verified the contents. Everything looked good and the kit was complete. Even before starting to put things together I made some notes on the layout diagram. I labeled all the parts on the diagram so that it would be easier and faster to "populate" the board.

My method for installing and soldering parts was to put the part in the correct holes, then bend the leads a little to keep it from falling out. I inserted every component of one type, then soldered all of one type.  For example, I installed all the 220 Ohm resistors in one step, then flipped the board over and soldered all them in the next step.  Novice builders may prefer to work with one part at a time.

Check things as you go along. After installing a part, I verified it was the correct value and that it was in the correct spot before soldering it. Note that some parts have to be installed in a particular orientation. Verify this as well before soldering.  Inspect every solder joint once it is done. I checked every solder joint of a component type after soldering all of that type. Really look close with lots of light and a magnifier if needed.  I only messed up one thing, I accidently broke a trace and had to solder in a jumper.

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CIRCUIT BOARD DESIGN SOFTWARE

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I too am building Mel's PCB circuit onto Stripboard after trying to get my head around different types of PCB layout programs.

I have found 2 wonderful programs to help guide me.  The first is TinyCad:- http://tinycad.sourceforge.net/Links.html   This is a free Circuit layout program, which also has its own group, here on Yahoo.

The second is VCad:- http://www.geocities.com/rogerlasau/VCad.html  This is also, a free program. (bless them all, I say :) )

This is a wonderful little Stripboard layout program that works wonderfully with TinyCad, which the creator, uses all the time. It 
also allows you to import Protel netlists, created in TinyCad, so that you know if your layout is correct.  Andy

CIRCUIT BOARDS:

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Low prices (for PCB's) : http://www.futurlec.com/PCBService.shtml  Emil Johnsen

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It`s a little more expensive, but I have had much better success with PCBs using positive image transfer film. It works like this: 1) coat the cleaned and dry copperclad with positive-etch polymer resin and bake in the oven (directions come with the stuff). Alternately. you can get precoated copperclad. 2) make a photocopy of the positive artwork, touching up any fuzzy edges with a black pen/marker. Copy this onto overhead transparency film. 3) in a dimly lit room (total darkness unnecessary), spray the copperclad with a little soapy water (I used a few drops of baby shampoo/pint) and lay the artwork transparency on the copperclad. Use a soft rubber squeegy (an old kitchen spatula works great) to remove all the air bubbles. -or- lay a piece of glass on the stack and lose the soapy water - your choice. 4) expose the PCB with a UV sunlamp at a distance of about 5 inches for 10 minutes. 5) using the developer solution, drop the board in and remove the excess polymer (this gets you a copperclad board with a etch resist coating of the circuti traces). Directions come with the solution. 6) rinse with water thoroughly. Etch as you would normally. Also, I seldom use ferric chloride etchant (the dark brown awful stuff they sell at radio shack). I prefer to use ammonium/sodium persulphate as an etchant, since it doesn`t cost as much when you make it yourself, it`s far less mess, it`s less toxic (not chlorine gas generated), and it etches much faster so your boards can have finer traces without undercutting. To make the stuff, dissolve 4 oz of ammonium or sodium persulphate (whichever is cheaper) in 2 quarts of warm water. When you etch, try to keep the tray of etchant/board heated to about 110F with a heat lamp. This greatly speeds the etching process (should take about 2.5 to 3 minutes tops). Ammonium chloride is available at most chemical supply houses or testing labs. They will ususally sell it to normal folks in small quantity, since you can`t make drugs or bombs out of the stuff (at least I don`t think.)  Gregg Pulley Geocrawler  12/16/97

COMPUTERS:

Park2.zip   -  DOS utility to move heads of hard drive off the data area to prevent damage when moving the computer.

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the program will not run on an XT computer. The program is compiled to use 286 or better code, plus the port settings and bios calls are all wrong.   Mel Bartels

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Q.  My motors run unevenly when I "slew" them.
A.  If they are uneven while slewing, then power saving features in the laptop or other device drivers running, beyond the control of scope.exe, that scope.exe is powerless to overcome, are the culprits.     mb

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power management and other drivers on the laptop will interfere with smooth operation   Mel Bartels

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A.  I can't see any effect on scope.exe. Any command sequence will not involve disk access so there will be no delay here. The only negative impact that I can think of is on the user side waiting for the program to respond.  Mel Bartels

A.  I have a LTE 5100 with v7.20 BIOS and my Power Management BIOS settings are Never in the Enabled Box, Custom in the Conservation Box, Standby Timeout: Never, Hibernation Timeout: Never, Drive Timeout: Always On, Screen Timeout: Always On.  With those settings my hard drive and screen have never turned off when using AC or an external DC source.  Don D'Egidio

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with scope.exe, a great deal depends on how many features you will have turned on. If you run without any error correcting or field rotation, you can get by on a 286 though a 386 is better. If you wish all the bells and whistles turned on, now, a 486 handles things nicely (I use old IBM Thinkpads for testing and they handle it  easily).    Mel Bartels

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disabling the power management features of my ThinkPad (760LD). After successfully turning off everything, I thought I would review the procedure, so at least it will make it into the archives.

1) Downloaded IBM ThinkPad utility file for DOS, uttpfdos.exe (vrs 4.22) (on my desk top computer), saving it to my 'desktop' which produces an icon on the desktop. Also printed out instructions for creating a disk image, and for installing on the laptop.

2) Clicking on the desktop icon opens a DOS window, allowing a disk image to be made.

3) Insert disk in LapTop. At the DOS prompt on the ThinkPad, typed uinstall, and the program loads itself.

4) At the dos prompt, type 'PS2 ?' and a help menu appears. You want to change the PMode settings to custom. Entering 'PS2 PMode custom' at the DOS prompt for both AC power and again for DC power.

5) Using the command PS2 ? Power, you should now see that it is in custom mode, if the custom mode is not already set to '00' time value,
you can do that here.

6) Then left computer on, and does not fall asleep at this time. QED  Bill Marriott   #6858
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Grabbed an old Compaq 286-12 laptop (weighs a ton!) from work, and got it to work pretty reasonably with the current 2/29/00 version of the software. Had to go down to 10 microsteps with PWM[] of 50 maximum, with resulting PWMRepsTick of 5. Max microstepping speed was about 250 arcseconds per second of time.          Mel Bartels

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...it is critical that the PMWRepsTick value be high enough for smooth motion. If too low, you can see and feel and hear the roughness as the motor responds to individual pulse width modulations. The PWMs must happen fast enough so that the motor responds to their average.  

So the PWM needs to be at least 10 and preferably 20 or more. Some motors like 50 to 100 or above. Turn off all the error correcting in the config.dat file. Make sure that you have no device drivers loaded on your laptop. Make sure that power saving features are turned off. Make MsPause and MsDelay 1. Make the PWM[] values a maximum of 100, and if necessary, divide all values by 2 to make the maximum 50. Even with a 286, you should be able to get 9-10 PWMs per tick out of the software.

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All of the systems I ship have run fine at 40 ms using the minimum computer specs I listed on my site. One system had to have the max pwm lowered to 80 instead of 100, but it was a 486-33. A 386 will barely support 20ms.   Lenord Stage

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there has been a lot of features added to scope.exe so using a 286 will tax things. It can sometimes be made to work if you turn off all features and error correcting, and set PWM repetitions per timer tick to 10 and use 100% current setting.  You can look for old versions of scope.exe circa 1995-6 that will run better on a 286.     Mel Bartels

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Q. I have an old 386 running at 16 MHz…

A.  This should work ok - make sure you have no device drivers running from config.sys or autoexec.bat. Be sure any power management in bios is turned off. Then set the PWM reps at 20 and see if you can get it to run at that rate. If not, try lowering a bit. Otherwise the motors will run rough. Mel Bartels 

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I have an 386/16 Laptop and while it works, I think it is the lower limit.    Berthold Hamburger  571

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A 486 dx and sx have the same pinouts. I have replaced an sx with a dx several times. If I remember correctly, a 486dx and sx are exactly the same chip except that the sx has the math coprocessor disabled (I think that this came about because Intel originally had some problems in the 486 production where the math  coprocessor came out bad and, instead of throwing them away, Intel decided to sell them as cheaper 486sx processors).  Al Peters  3061

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The 386 came in two varieties. The DX and the SX

The way tell the difference is that the SX fitted into a socked and had the connectors along the edge of the chip (All four edges to be precise). The main chip the 386 part was usually soldered to the motherboard. The DX version was the same sort of chip as the later 486 ie pins underneath which fitted into a socket. Zero Insertion Force sockets weren't about then, so lots of pressure had to be applied. (Lots of bent pins resulted as well). 

As for co-processors "both" varieties had co-processors available (this was the last cpu to use separate processor / co-processor setup. The later 486 SX had the co-processor disabled, but it was on the chip. The 487 chip was a full processor with FPU enabled. 

The 386DX co-processor was the pinned type and the SX a edge connector socket type.  Dave Cook 6221

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You can run the Windows 3.1 or DOS version of MSD (Microsoft Diagnostic) It should tell you if you have a Math coprocessor present. The program should be in the Windows or DOS directory.   Dave Bevel  3873

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Q.  The backlight on my laptop screen went dim, then out.  Anyone know where I could get a replacement light?  

A.  Lookup "Cold Cathode Fluorescent Lamp" at Digikey (http://www.digikey.com)

You'll have to compare the dimensions of your existing lamp with the burned out lamp, and it will probably take some soldering.  I did it a couple years ago with a Dell Latitude.  The replacement lamp was even brighter than the original.   Brad Davy

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3.5 Rounds Per Second MaxDelay 1500  MinDelay 1000   HsTimerFlag 1   

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When I went to load it on my laptop I found the darn floppy had died..... I found my old 100mb parallel port zip drive, so thats the "new" floppy for my laptop!  NEVER throw anything away!!!!!!!! :-)  Chuck Shaw

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With laptops, the output from the ac adaptor is 18 volts, but that is to charge the 12v internal battery. The input voltage is stepped down well below 12v for the board and drives.  My laptops run fine off a 12v input.  I just cut the business end off of an extra ac adaptor and wired it straight to a 12v battery.   Polarity matters.  Ben Davies 

CONNECTORS:

Serial Port                

Null Modem Pinouts

+++

A.  Signal ground, transmit and receive should be all the lines needed. For a simple null modem just wire transmit to receive and receive to transmit.   Marty Nemi

COORDINATES:

InputEq->Alt  converts input equatorial to input altazimuth. This menu selection calculates input altazimuth coordinates based on input equatorial coordinates. Used for encoder only and other situations where the scope is moved such that the current altazimuth coordinates match the input altazimuth coordinates. Mel Bartels

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+++

+++

(for an equatorial mount)...azimuth of zero means being on the celestial meridian while facing away from the pole.  Mel Bartels 13219

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The declination in a perfectly aligned equatorial will equal the altitude reading.      Mel Bartels

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Home coordinates are for parking your telescope - not setting where the telescope is. For instance, if you want to park the scope at the zenith, and it is an equatorially mounted scope, enter home altitude equal to (90 - your latitude), and enter home azimuth of 0.    Mel Bartels

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equatorial telescope: altitude is same as declination, azimuth same as hour angle (degrees east/west of meridian however, when you do the gem meridian flip declination is now mapped to altitude so that 

dec = 90 = alt = 90 
dec = 45 = alt = 135
dec = 0 = alt = 180
dec =-45 = alt = 225
notice how dec now travels in reverse compared to altitude and azimuth is mapped to hour angle with displacement of 180 deg

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CURRENT LIMITING RESISTORS:          also see overvoltage

In our quest for speed in slewing mode, we operate the motors at a much higher value than the rated value specified by the manufacturer. Some use 24V, others, like myself use very low voltage stepping motors with a 12 V supply. The performance is directly in proportion of the amount of overvoltage to the motors, 2X,3X,5X, 6X and so on, within reasonable limits however. To my experience so far, 7X has been a maximum limit. I used 1.9V motors with 13.6V.(lead acid battery) That looks good, but it will introduce new problems. Let's look at this last motor. It has 0.5 ohm resistance per windings. If fed directly to 13.6V it could pass a PEAK current of 27A, per windings. Under these conditions you would fry your transistors, PCB, the motors, very rapidly.  That is why I designed the current limiter, to keep the current flow to a preset value no matter what voltage is present.  Experience with the circuit tells me that a current between 2 and 3 amperes  is an ideal choice. That makes R2 anywhere between 0.3 and 0.2 ohms.  I recommend to use the limiter with motors having a nominal operating voltage below 4 volts. Of course if they are operated from a 12V supply.  With 24 V operation the limiter should be used with motors of 8 volts or  less.  With your 6V, 1.2A motors, you need no limiter if operated from 12V.        Jean-Charles Vachon  2928   http://www.bbastrodesigns.com/currentlimit.html 

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Q.  the resistor is placed between the dc supply voltage and the lead going to the transistor from the stepping motor.

The series resistors draw a great deal of wasted power and needlessly drain batteries. They do have the advantage of lowering the motor's inductance which can increase highest speed.  The current limiting circuit option should be used in place of the resistors when overvoltage is greater than 3x.  Mel Bartels

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Q.  When I use the Jean-Charles_Vachon__Preferred_current_limiter.PDF circuit it works as advised limiting the current to 1.5A when I use 12V using a 0.4 Ohm resistor. But when I use 24V the curent goes up to more than 3A. 

So the circuit is not automatic about voltage changes? Why the original PDFs dont talk about it? there are any variation that is really automatic?

A.  The circuit should limit the current to a voltage drop of 0.6 - 0.7 volts across R2, meaning about 1.5 A for 0.4 ohms - after that, the transistor would turn on and divert the base current of the TIP127. 3A should drop 1.2 v, can you check if it does? If so, check the base voltage of the MPSA56 - if more than 0.7 V, it must mean that this transistor is gone. 

Have you checked that the TIP127 is inserted correctly? I Googled and found this: <http://www.cdcc.usp.br/cda/telescopios/hp-mbartels/altaz/currentlimit.html>  where the TIP127 is shown obviously the wrong way! There is a reverse diode inside that will pass current nonetheless, but the limiting won't work. Nils Olof Carlin
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I'd located the current limiting resistor in the 24v line supplying both motors. Either motor would run fine on its own, but when running together, the Azimuth motor would stall. When testing, I'd used the handpad to move around - which can only move one motor at a time. Slewing under the stars, I'd not seen or heard the stalling, as the other, louder, motor was still running. Due to my gearing, the altitude movement is quick, so stalling in azimuth was just for a short time... but enough to fubar me. 

Finding the problem was a bugger, but the solution is simple. I added gave each motor its own resistor and the stalling is a thing of the past.        Mark Rice 10832

+++  

I calculated that 80 ohms would be needed, but couldn't get this to work.  After hours of experimentation using a resistor ladder (resistance wire from an old electric blanket) I found a that using 33 ohms works great...  But the tolerance is pretty tight. Anything below 28 ohms causes stalling at speed and anything higher than 37 causes stalling at the start of the slew.  Jean Charles Vachon's circuit is probably a better way to go, but whatever  approach you take, it is WELL worth the effort to get right.  My slewing speed is 3 times what it was a week ago :))    Mark Rice   5996

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The resistance value of the series limiting resistor can be calculated with this equation:

                   Ro = ((Vs - Vd) - Vm) / Im

WHERE: Ro = Series resistor value in ohms.
       Vs = Motor coil supply voltage, larger than Vd + Vm.
       Vd = Voltage drop from transistor & diode, about 1 to 2 volt.
       Vm = Rated voltage for motor when stopped.
       Im = Rated current (amperes) for motor when stopped.

                 Rw = ((Vs - Vd) - Vm) * Im

WHERE: Rw = Series resistor value in watts.
       Vs = Motor coil supply voltage larger than Vd + Vm.
       Vd = Voltage drop from transistor & diode, about 1 to 2 volt.
       Vm = Rated voltage for motor when stopped.
       Im = Rated current (amperes) for motor when stopped.

With this information in mind it becomes clear that stepper motors with very low voltage ratings (Vm) are highly desirable

Greg Granville http://users.adelphia.net/~greg_gran/bigdob.html#Lessons 

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....simply put 10 ohm, 2W current limiting resistors in series with the motor windings and that seems to work very well. I had planned on experimenting with resistor values, but my first guess seems to work well. I can run the motor supply voltage up to about 17V (I'm afraid to go higher as I might overheat the 7805 5V regulator) which gives me a slew speed of roughly 2 degrees/sec, with smooth microstepping and no noticeable motor heating. I'll still be experimenting with the MS settings, higher resistor values, and higher voltage at my leisure, but I've found a workable solutions for the slow slew problem that had been bugging me.         Steve Rivet  6029

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I put series limiting resistors according to the excellent Greg Granville's Homepage. It works wonderfully on a Pentium II computer, but when I use a 486 66MHz, the resistors are turning very hot (unable to touch them).  It happens even without running the motors (as I run the handpad test routine, for example). In slew mode, the resistors were very hot too. I'm using a 3.5A 12V power supply and 5.4V 1.5A motors. 

+++

The current limiting resistors for the motors would be in series with the motor power leads. These are separate from the resistor to provide minimum load for the AT supply, which is in parallel with the 5V load.  Steve Rivet  8458
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My six volt steppers are driven at 24VDC, with 10 ohms series resistance. Small flywheels are directly coupled to the stepper shaft. What is my value of MinDelay in config.dat for halfstep slewing? 200   Tom Krajci    1335

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... the current flow through a stepper (during conduction or the power phase) is very simple! It is a ramp - the slope of the ramp (di/dt) is equal to the applied voltage divided by the inductance of the winding (V/L) - very simple - and very obvious on a scope.

At high slew rates the inductance limits how high the current can go - the resistance has nothing to do with it. The standard equation for the current .... If = Ii * ( 1 - e ^ (-R*T / L)) does not apply (actually it does, it is correct BUT the resistance is more than 2 magnitudes different from the inductance so the inductance is by far the dominating effect - again as seen on a scope trace - straight ramp! not an exponential). Plug the values in, say 1800 RPM, 1/2 step, 30mH and you get 177mA peak !  Gary Myers   5344

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I use 6V steppers on my sixteen inch scope, driven at 24V. the motors have 10 ohms series resistance to help limit current during the ramp up/down portion of halfstep slewing (at max slewing speed, back EMF limits current, so the resistors do the important job at slow motor speeds while slewing).

PWM settings will help control the amount of current to your motors.  Normally, while tracking, you'll find you don't draw much current from your motors. When slewing, you'll draw 1-2 amps for a few seconds while they ramp up/down for the short time that they are moving at slow speeds...after that they will draw about as much current as when they are microstep tracking.      Tom Krajci    6166

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Q.  What is used to determine the current percentage? Is it the motors voltage rating and the voltage used to power them? I'm thinking that if 6V motors were powered with 6V, then the current percentage would be 100%. A 6V motor powered with 12V would be 50%. Is this correct? 

A Correct. Also, during microstepping, you usually don't need all the torque that the motor can deliver, so you can reduce current percentage down by another half often. This makes noise quieter and saves battery.  Mel Bartels

CURRENT COMPENSATION:

+++

Do not confuse individual winding current compensation with quarter step correction.

The former corrects for variations in output current from a circuit board, while the latter corrects for variations in step size in the motor. The former will make consistent sized microsteps across all four windings easier to achieve, while the latter makes even sized fullsteps easier to achieve.       Mel Bartels    6745

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To measure the current you need to separate out the flyback current and the transformer action current that is generated. This is relatively easy to accomplish. The way I did it was to cut the track under the board that goes to the collector of each output device. Now insert a small value resistor in series with the collector line back to the original point (the motor/diode connection). the current can now be accurately measured by measuring across the resistor. I use 0.1 ohms and use a DPM (0-200mv) this gives me a full scale reading of 1.999A. Then go to single step and step it through measuring and recording each step on each phase. Stick these in a spread sheet (I have one that given the current values shows the expected position and position error).   Gary Myres    5191

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Step 0 - I made a breakout cable with DB9 connectors to allow me to tap into the motor wires between the circuit board and the motors.  The returns are soldered together (no break). Each coil wire has a bullet connector that can be separated allowing me to connect my digital ammeter in series each of the 4 windings.

Step 1 - I use the MSParms +/- keys to advance the motor windings from a0 - d0 using the scope display to determine what coil is energized.

Step 2 - I step through each of the windings a0 - d0 and record the current for each winding.  

STEP CURRENT Compensation Current w/comp in config
a0 .501 .433/.501=0.864 0.29
b0 .478 .433/.478=0.906 0.459
c0 .433 1 0.200
d0 .485 .433/.485=0.893 0.210

Step 3 - I calculate the required compensation as shown in the table above and put the compensation factors into config.dat for each axis

For example, the following were used tro compensate for above currents:

PWM_A_a_Comp 0.864
PWM_A_b_Comp 0.906
PWM_A_c_Comp 1
PWM_A_d_Comp 0.893
Larry Bell

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For instance, if one finds that the 2nd output line ('B' winding of the altitude/declination motor) reads a low current compared to the other output lines, the other lines can have their output current lowered by the software to compensate. Default is no compensation and config.dat does not need to be changed. If you wish to use output line/motor winding current compensation, add the following variables to config.dat. A value of 1 means output 100% of available current, a value of 0.5 means output 50% of available current, and so forth. The values appear in config.dat as follows (this example shows a compensation for a disparate 'B' winding of the altitude/declination motor):
PWM_A_a_Comp 0.8
PWM_A_b_Comp 1
PWM_A_c_Comp 0.8
PWM_A_d_Comp 0.8
PWM_Z_a_Comp 0.8
PWM_Z_b_Comp 0.8
PWM_Z_c_Comp 0.8
PWM_Z_d_Comp 0.8             Mel Bartels

+++

I believe we are on the same wavelength. While I was adjusting the microsteps I noticed variations in the current draw on each MS. When I did the measurements of the full steps I sent in I also noticed variations, say (for the sake of numbers) a0=.175ma, b0= .180ma, c0=.240ma, d0=.260ma This is what I would use for the QSC...bring down b0, c0, d0 to equal or be near a0. Correct?

Not correct.

Use the current compensation to bring the current as measured for A0, B0, C0, and D0 to the same level. Use the config.dat vars

PWM_A_a_Comp 0.8
PWM_A_b_Comp 1
PWM_A_c_Comp 0.8
PWM_A_d_Comp 0.8

PWM_Z_a_Comp 0.8
PWM_Z_b_Comp 0.8
PWM_Z_c_Comp 0.8
PWM_Z_d_Comp 0.8

Here a low B winding on the A motor is being compensated for.

After adjusting for even sized microsteps within each fullstep, use the QSC to correct for step spacing

QSC_a0 0 : 0
QSC_a1 0 : 0
QSC_a2 0.1 : 0
QSC_a3 0 : 0

This compensates for the A motor moving too far for the 'a' winding by 0.1 fullstep halfway through its range.  Mel Bartels

+++

Another way to simulate the effects of current compensation (though it will necessarily apply to all windings) is to increase the MaxPWM but leave the PWM[] values as they are. That lowers the apparent current by PWM[0]/MaxPWM. So if you double MaxPWM, you lower the current by half (for all windings). You might see if this creates the current that you are expecting.   Mel Bartels8500

DAT FILES                     http://www.bbastrodesigns.com/operate_data_files.html  

+++

I uploaded 06bstars.dat in the files part of this group. It contains 06 bright stars, meant for use with slow slewing telescopes. 
Positions are epoch 2006, and I tried to find stars so that they are never more then 10 degrees parted from an other bright star. The stars I chose are for use from +50 degree latitude and above. I ordered the stars by their constellation name, and in alphanummeric order.   Marc Fokker   (change the DataFileCoordYear variable in Config.dat to 2006.0)

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go to the File menu and highlight the DataFile, Hit the enter key and then select a file from the sub-menu by hitting the key corresponding to the letter of the file I want (for instance bstars) then hit the letter key corresponding to the specfic object I want. The menu screens go away and it returns to the main scope drive program. The screen shows in the bottom section on the lefthand side the File name, BStars.dat, Object name (what ever object I pick), and in the middle section above this, in the Input section in the Ra and Dec lines, it shows the coordinates of the object. The current coordinates are where the scope is now pointing and the input is where it will goto. I am running in EQ mode and my Alt and Az Inputs show the same as the Current (I guess they are supposed to). If I then go to the Move menu and hit enter with the Equat (move to input equatorial coordinates) highlighted, the software makes the goto move.  Steve Mitchel

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Using data files:    Press 'd' to select an object from a data file. Press '1' to move to equat. (GoTo selected object)  The scope will slew to the new object and start tracking.  Kelvin  

+++

Q.  ability to browse through a database file up and down (PgUp and PgDn keys) would  add a lot of ergonomy to object selection.

DRIFT:

periodic error usually dominates drift by an order of magnitude   Mel Bartels

+++

Drift is independent of PEC. That is, the PEC depends solely on the motor shaft rotation angle. What the scope via the software is doing with drift and alignments is something else entirely.      Mel Bartels

+++  

The drift calculation in scope.exe works like this: change or drift in position / (guiding end time - guiding start time) So, drift has typically a rather large error range because the positions at the start of guiding and at the end of guiding must be very precise since the time period for the guiding is usually rather short.  Also, any errors that accumulate or change during this time like Periodic Error will adversely affect the calculation if the guiding is stopped at a different point in the PE cycle than when it was started.  Hence, though not in real time, the drift value obtained from the routine that handles guiding efforts translated into periodic error curves is perhaps most accurate. When guiding is finished, there are two options that scope.exe gives you:

1. stay where you are currently at

2. revert back to where you would have been as if you had never guided    Mel Bartels 10578

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Scope.exe, if tracking is left on, will return to the last tracked to position after drift input is finished. Mel Bartels

+++

Q.  I thought I understood how to adjust for drift during tracking, but now I'm not so sure... Please could someone explain?

A. Just put the handpad into a guide with drift mode, then after recentering after a period of time, hit the right mode key to update the drift. Mel Bartels

A.  For just trimming out drift, you do not need to autoguide to get it accurate.  Simply get into guide mode (not guide+save) and maybe sure that drift update is enabled (on) via the handpaddle menu. Center the star on a crosshair, turn on guide mode, and periodically recenter it. After a couple of minutes, exit the mode and the drift will be calculated and updated.  Chuck Shaw

+++

Turn off drift updating via menu option handpad|update drift.

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The two principal errors affecting guiding accuracy can be fixed at one time: the periodic error of the gear that the stepper connects to, and drift. The drift may need to be tweaked after pointing to another section of the sky.

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To track the moon, put in a drift rate that mirrors the moon's rate across the sky. For instance, the moon revolves around the earth in 27.3 days or 53 min/day, or 2.2 min/hr. That's the drift rate to enter into the drift right ascension field Mel Bartels

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Let me give a real example how I work:
In preparation of a series of exposures I calculate the expected drift setting with the help of a program a friend of mine (Helmut) has written. It calculates the "Kings Rate" for the desired celestrial position. I set this calculated drift value to the Az Drift in Scope.exe. Lets say this time its -2.300. Now:

* Set AZ drift to -2.300
* I take 3 exposures of 5min each
* These 3 pictures show a further drift of 2" from the beginng to the end (3x5min+download = 17min)
* I calculate the drift delta from the images to be 0.1176"/min
* Now I adjust the drift setting via the menu Coord -> DriftAltAz to -2.4176
* Finally I take my desired exposures which now show almost no drift

My desire is now to get this delta of 0.1176 applied without stopping and repositioning the scope (which happens during normal keyboard entries).  Rolf Apsitich

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menu option to turn off automatic drift fields updating when in handpaddle guiding modes. This is displayed as either DUon or DUoff in the handpaddle display area.                Mel Bartels

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Q.  My problems relate to accuracy. My mount is not accurately polar aligned (a long story...) As a result I have quite a bit of drift and longer slews will result in the object being out of the field.

A.  You have two options: do a full 2 star init so as to align your scope correctly with the stars, or, do the equatorial startup, and let the  software calculate drift for you by doing a little guiding (this will have to be repeated for different parts of the sky, but you can do this as you observe)..... Just put the handpad into a guide with drift mode, then after recentering after a period of time, hit the right mode key to update the drift.  mb  7321

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Changed accumulated drift reset so that it does not occur when drift values are updated. It is now up to the user to keep track of accumulated drift and to zero it out via the menu option when desired.  Mel Bartels  10102

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A.  Depends on your mount type - if altazimuth then resetting to equatorial coordinates implies that your altazimuth coordinates are no longer perfect.  Using guide to calculate drift is independent of resetting coordinates. It makes for more accurate tracking but not necessarily more accurate gotos.Mel Bartels

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ENCODERS:       http://www.bbastrodesigns.com/encoders.html     http://www.bbastrodesigns.com/operate_encoders.html          http://www.melbartels.com/larrystrange/invention.html

The fundamental problem with viewing accuracy from the direction of a planetarium program + encoders is that you are limited to encoder accuracy. Knowing that encoders may be +- 1 or 2 pulses, and that each pulse may be several arcminutes to many arcminutes, the pointing accuracy will always be fairly unable. If encoder is 2048 quad decoded to 8096, accuracy is maybe +- 10 arcminutes. Acceptable pointing accuracy visually means never having to remove a high power eyepiece.

So it is best to let scope.exe keep track of the positioning. Attach the encoders to scope.exe. Scope.exe uses encoders to coarsely close the loop 1 per second. Encoders really only come into play if you slip the scope manually, or move it manually on purpose.  Mel Bartels

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Use the move/halfstep menu option to move the telescope a set amount of halfsteps.  Assuming fullstep size of 3 arcseconds, and ability to measure angle change down to several arcminutes (8192 count per revolution encoders, or precision bubble), then execute at least 5,000 steps for 1% accuracy.  If encoders are used, the program will automatically display the fullstep values for AltFullStepSizeArcsec and AzFullStepSizeArcsec that you should enter into the config.dat file.  Try for 0.1% or 1 part in 1000 accuracy (move at least 50,000 steps, or roughly 45 degrees). Mel Bartels

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Q.  Am I correct to presume that the highest resolution encoder must be placed on the altitude axes because you only use 90 degrees on this axes so a one step of the encoder on the alt axes could de-orientate scope faster than the same step of the encoder on the azimuth axe?

A.  My Alt/Az system uses rollers, and the Az system seems to accumulate more errors than the Altitude system. When you slew, the number of degrees you slew is quite often a lot larger in Az than Altitude so if there is a tiny bit of slippage (I think someone once called it "microslippage") it would accumulate more in the axis that was moving the most.    Chuck Shaw

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You can tell if an encoder is hooked up backwards by moving the scope and watching the count....they should be increasing to the west and north   Steve Mitchell

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Encoder counts are ignored during slew       Mel Bartels

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The serial port baud rate affects how fast scope.exe can query and listen for answers from the encoder interface box. How fast the encoder interface box can count encoder pulses is an entirely different matter.   Mel Bartels

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I don't know exactly what the sampling rate is for the board, but it's probably between 1000 and 5000 samples per second.   Dave Ek.

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The command that scope.exe sends to the encoder box is very simple: typically a 'Q' is it. This depends on the box. Then the encoder box, after a short delay, returns the counts on each axis. So it is very simple.  Mel Bartels

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The software is hardcoded based on encoder type to return the proper value when going under zero. Depending on encoder type, it will read either max-1 or –1   Mel Bartels

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q)  I slew to an object and after it seems to complete the slew it goes backwards then forwards then backwards then.... well you get the idea.  The slew message say ResEncoder 23 or something to that effect with the number changing .

a)For some reason, the encoder counts are not keeping up in real time. 

Res Encoder 23 means that the telescope has been reset to the encoder position 23 times.  You can delay the encoder read a bit by increasing the SerialWriteDelayMs value to whatever it takes.  This is the value that the read will occur after the query is sent in milliseconds.

Now, if your encoder mounting is bending or warping slightly, then the encoders will oscillate, and no software fix will work. Mel Bartels

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I take it as a rule of thumb that the position is probably accurate to 1-2 encoder counts, but can be off by as much as 4 counts. Gearing the encoders introduces more errors to compound the situation, and consequently I do not recommend gearing more than 4x.  Mel Bartels 2659

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coordinates|convert  converts input equatorial to input altazimuth. This menu selection calculates input altazimuth coordinates based on input equatorial coordinates. Used for encoder only and other situations where the scope is moved such that the current altazimuth coordinates match the input altazimuth coordinates. Mel Bartels

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EncoderErrorThresholdDeg             TrackEncoderErrorThresholdDeg 

When movement is being done with halfstep slewing, then the slewing encoder threshold is used, whenever movement is being done with microstepping, then the tracking encoder threshold is used. Mel Bartels

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Added new menu item that steps through each microstep of every winding, recording encoder values at each microstep. Readings are saved to a file called TRENC.TXT. By attaching a precision encoder to the stepper motor output shaft, a series of values can be obtained displaying smoothness of motor rotation. Look for track encoders under the menu section move. If you reduce microsteps to 10 per fullstep, use a 200 step per revolution stepper, and attach a 8096 count per rev encoder, you can get 4 counts per  microstep.              Mel Bartels

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In scope.exe, the encoders are used to close the open loop steppers once every second. That means that every second, the encoders are read and the motor position and encoder position are compared. If the encoder and motor positions disagree, the encoder position is adopted. The threshold of disagreement that will trigger then positional reset to the encoder position is set in config.dat:

EncoderErrorThresholdDeg         TrackEncoderErrorThresholdDeg 

There are two thresholds because you may wish the threshold to be very tight during slewing but relaxed during tracking, or visa versa.  There are several good reasons while operating a telescope that you wish the thresholds to be tight or lose, depending if you are slewing or tracking. Setting the thresholds to 0 de-activates them. Mel Bartels

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The encoders update the scope position once a second. However, the encoders are rather coarse, measuring in arcminutes while the stepper microsteps are measured tenths of an arcsecond.   If tracking is on, the encoders will force the telescope to return to its original position. If someone bumps the scope while looking through the eyepiece, the object will be recentered. If tracking is off, the encoders will indicate the new position the telescope has been pushed to.
I like to keep the slewing encoder value tight or small so that if there is slippage, the slewing will still conclude accurately. The tracking value I like to keep looser or more open so that the object doesn't jump suddenly in the eyepiece in case the encoders slip.          Mel Bartels

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The threshold values are in degrees.  So 0.1 is a much tighter tolerance than 1 degree.  Don't make it the same resolution as the encoders though, because encoders have some inaccuracy in them.  Usually I suggest best or tightest tolerance at twice the encoder resolution.  So in your case, about .12 deg.  Mel Bartels

EncoderErrorThresholdDeg .1

TrackEncoderErrorThresholdDeg .1

The upper value controls the reset for slewing and the bottom value for tracking.  So you could leave encoders attached and set these numbers to impossibly high values like 360.  Otherwise, when encoder vs scope error reaches these values, the scope resets to encoder counts.  This is for hand bumping or moving of the scope

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The variables EncoderErrorThresholdDeg and trackEncoderErrorThresholdDeg control the allowable difference between scope and encoder coordinates before a reset to encoder coordinates occurs. There are two variables since a tighter tolerance during slewing to a target position is often desired compared to the tracking reset tolerance.  Set these to a value that represents at least one if not two or more encoder counts. At any time the scope can be reset to encoder coordinates via the 'reset to encoder menu option'.  When a reset to encoder coordinates occur, if you wish encoder these threshold violations to be recorded, set the config.dat variable MakeEncoderResetLogFile to 1.Mel Bartels

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...set EncoderErrorThresholdDeg to a value of 2X the resolution of the encoders and leave TrackEncoderErrorThresholdDeg at zero, this will slew based on the encoder values and not update the scope position during tracking. i.e. not jump to a new position if the error threshold is crossed.  Marty Niemi

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The encoder offsets as recorded in config.dat, and used in the software, are the offsets or differences between the encoder position as determined by the raw counts and the actual position. For instance, you may initialize the encoder with the telescope pointed at 45 degrees. The encoder count says zero but the scope is actually at 45. So the offset is 45 degrees, stored and manipulated (as all values are) in radians, here 45 degrees is 0.785 radians. Let the software calculate these values for you.   Mel Bartels

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The values are saved in config.dat so that you can recover your scope's position in the following circumstance (happens to me a lot): scope is aligned, then powered down at sunrise, LEAVING the encoder box powered up.  This takes very little current draw. At next use (can be in daytime, to do some daytime viewing of planets and brighter stars, or, at night), I start up scope.exe and say yes to reuse encoder position. That way, if I move the scope around during the daytime, the powered encoder box knows about it. Now I don't need to re-init or do anything special.   Mel Bartels

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Q.  What is the upper limit for encoder resolution? Is it possible to modify the software to increase that limit, or is this a hard limit....?.   brad davy

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The 'limit' of 65535 or 16 bits or 2 bytes is more an external limit based on many encoder interface boxes  ability to return no more than 2 bytes of position information. Scope.exe can deal with counts up to 32 bits.

People often ask, "What is the encoder count resolution possible?". The answer is often 16 bits based on the popularity of encoder interface boxes available. This is a limit that the encoder interface boxes impose.

If you wish to build (or in this case take advantage of the mouse driver) you can go up to 32 bits. Mel Bartels

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A. The only problem with such resolution on the encoders is if you move the scope too fast, you can drop counts if the interface box is not interrogating the encoders as fast as the counts are clicking by..... You should not have a problem though using motorized slews. My GEM has 1440:1 (360worm and 4:1 spur gears) and the slewing is plenty fast to suit me. I kinda like to just sit and watch it and marvel at what all is going on!!!!  Chuck Shaw

 A. I don't know exactly what the sampling rate is for the board, but it's probably between 1000 and 5000 samples per second.   Dave Ek.

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Q.  Does resetting to "Encoders" also loose PEC sync?

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Scope.exe uses the raw encoder counts. Scope.exe handles all the coordinate conversions plus a lot more, so encoder box functionality beyond delivering raw encoder counts is ignored. The encoder box is free to be played with as one desires, as long as the encoder count is not reset in some manner behind scope.exe's back. 

Scope.exe reports the raw encoder count so that you can see how the encoders are working.   Mel Bartels  4346

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The MGIII is based, I believe, on the MGI design, which is a stand-alone unit (no computer required) which does all the transformation calculations itself and includes its own display. The MGI uses a real CPU chip ("a highly integrated version of the Z80") along with EPROM memory. This was undoubtedly done in the MGI to support floating point computations. The MGIII uses the same circuit board as the MGI and a subset of components.  This is probably a case of reusing a design that the designer was familiar with.

Microcontroller chips are an ideal solution to problems involving hardware interfacing. They are very easy to program. They are, essentially, a microprocessor and RAM in one package. Microcontrollers are not as well suited to applications requiring floating point computations, but simply tracking encoder counts doesn't call for floating point.

I chose to use a PIC16F84 because the hardware required in order to program it is very inexpensive (less than $10 if you build it yourself). There are more well-suited PIC chips available for this task (some have built in serial communications, while I had to program serial comm in software in the PIC16F84), I didn't have access to the programmer needed for them. This, incidentally, is my first microcontroller project.  Dave Ek  808

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EQUATORIAL PLATFORMS:

The addition of a field rotator on a reasonably sized newtonian is NOT a big deal (see my set up at http://www.ghg.net/cshaw/frsys.htm ). The problem, as you mentioned is dealing with the guidescope rotation...... If you do not compensate for that, you get a translation error introduced.  The solution to THAT issue has several paths...... if you use a Starlight Express or an SBIG camera with a self guiding feature (i.e. the interlaced Starlight Express, or the dual chip SBIGs) the problem is moot. I used an ST-9 and it was a snap to get perfectly guided images.....(http://www.ghg.net/cshaw/st9-1.jpg). Another alternative to avoid guidescope rotators is to simply use the old standby, and off axis guider (I hate those things, since its often a lot of hassle to find guidestars, but it works GREAT!)

Or, like you say, do not worry about it anyway if you can get 30 sec images unguided. Problem is, to soak up enough photons, you will need to take a LOT of those images and average them.... Today's software allows you to translate and rotate images during that process to properly align them, with the result you lose a small amount of sharpness, and you lose the "corners" of the images (no problem unless the target fills the whole frame) Lots of options! You won't really know which one works best for your needs till you start trying them!!!! So lets start hearing about your progress on building your system!!!!! <grin>   Chuck Shaw

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...the equatorial table as invented by Poncet et al is very limited in usable latitude and needs to be precisely aligned for serious imaging. In addition field rotation is introduced when guiding corrections are attempted.  Mel Bartels

ERROR CORRECTION:

PEC    Z1Z2Z3    ANALYSIS FILE    DRIFT    POINTING MODEL CORRECTIONS    REFRACTION  

As a general rule, error correcting in scope.exe is always absolute, never relative and never cumulative. Mel Bartels

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Scope.exe has lots of error correcting built in. You can use a combination of TPoint and scope.exe's error correction in tandem, but don't let both  programs work on the same kind of error. For instance, use either scope.exe or TPoint's error modeling, but not both, as the programs will chase each  other. I have found it best to let scope.exe handle the dirty stuff, ie, error correcting, and let it report the finalized best coordinates back to the planetarium program. That's because scope.exe already has the coordinate transformation running, to convert telescope to sky coordinates. These sky coordinates are then reported back to the planetarium program. If the planetarium program is running error correction, then it likely is using a rotational matrix of its own. In practice, having one set of routines undo what another set does, causes creep in coordinates (usually very very tiny), kind of like a random walk.    Mel Bartels     8555

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Errors to either eliminate by better design and construction, and further by software compensation in order of importance and in order that they should be tackled:

gear backlash
gear periodic error correction (called PEC)
for stepper motors, physical variations in the quarterstep spacings over the sequence of windings (called QSC for  QuarterStepCorrection)
drift
guiding corrections
atmospheric refraction
precession
discrepancy between the optical and mechanical axis in the vertical axis (called Z3 or altitude offset)
axis misalignment (one side of the rocker is higher than the other) (called Z1 or axis misalignment)
discrepancy between the optical and mechanical axis in the horizontal axis (called Z2 or azimuth offset)
altitude vs. azimuth error correction (dobsonian rocker base levelness) (called ALTAZEC)
altitude vs. altitude error correction (tube droop, altitude bearing unevenness) (called ALTALTEC)
azimuth vs. azimuth error correction (azimuth drive gear eccentricity) (called AZAZEC)
nutation
annual aberration
residual errors, captured as pointing model corrections (called PMC)

Mel Bartels

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9 Save CONFIG.DAT so all settings are remembered. (I'm also not sure this is necessary since error corrections may be saved automatically as they are generated.            Mike Makowski

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.  Which factors change with the transportation of the scope and which not? Which parameter can be once initialized and which have to be made everytime the scope is built up..errors are:

gear backlash - will not change

gear periodic error correction (called PEC) - may change if you play with the motor and gear mountings during assembly of the scope

physical variations in the quarterstep spacings over the sequence of windings (called QSC for QuarterfStepCorrection) drift - will not change

atmospheric refraction - compensation in real time

axis misalignment (one side of the rocker is higher than the other) (called Z1 or axis misalignment) - does not change

discrepancy between the optical and mechanical axis in the horizontal axis (called Z2 or azimuth offset) - depends if you recollimate

discrepancy between the optical and mechanical axis in the vertical axis (called Z3 or altitude offset) - depends if you recollimate

altitude vs. azimuth error correction (dobsonian rocker base levelness) (called ALTAZEC) - must reassemble with rocker and base in same orientation

altitude vs. altitude error correction (tube droop, altitude bearing unevenness) (called ALTALTEC) - ???

azimuth vs. azimuth error correction (azimuth drive gear eccentricity) (called AZAZEC) - will not change if rocker and base in same  orientation

residual errors, captured as pointing model corrections (called PMC) - hmm, might want to compare a few nights to each other to see

Mel Bartels  5507

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AZAZEC, or AZimuth vs AZimuth Error Correction. This is an azimuth correction based on azimuth. Best used for azimuth gear eccentricity and similar errors, it should not be used for azimuth errors of tilt that increase with altitude.  Use the Z1Z2Z3 group of tilt corrections instead. The new variable UseAzAzECFlag is used in the config.dat to turn on the EC at program startup, exactly as ALTALTEC and ALTAZEC. The file AZAZEC.DAT holds the corrective values.  Mel Bartels

FLYWHEELS:

my tinkering and reading causes me to come to this conclusion: Most ATMsystems/stepper motors drive such a small angular inertial load that the addition of small flywheels is almost mandatory to avoid high speed resonance problems. (Mine were simply two inch square pieces of 1/4 inch plate steel...and my motors are NEMA frame size 23...that makes their body about 2 1/4 inch square.)    Tom Krajci

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…had problems with stalling during half-stepping, like you are.  I found that an old plastic 4" Peanut Butter lid friction fit onto the stepper shaft made a great impromptu flywheel, and had an incredible effect on Half-Stepping! I will Admit, I spent WAY too much time playing with various sized Flywheel and Weight combo's, just to see how fast I could spin that stepper      James Lerch

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I found that flywheels, in conjunction with series resistors, really helped me get my slew speeds up higher. Also, I run my 6V steppers at 24V...and my 5V regulator (with heat sink) has not had any problems.    Tom Krajci   6054

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I found that loosely coupling my particular flywheels works better than a solid connection. I filled a 1.25 od x 1.5 h alu tube with lead and bored it to fit slide over the outboard worm shaft on my reduction boxes (so it is essentially coupled to the stepper.)  When ramping, the flywheel slips or lags behind the shaft.        Jay Leblanc

This is a very good idea, particularly because it will help the situation with microstepping, when the motors are asked to jump instantly to a high microstep speed.     mel   45

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I designed a viscous damper for a Cartesian robot several years ago and it has hundreds of millions of hours of useful service on some very expensive industrial robotics and automation.
 
Imagine a light, hollow donut with a steel ring inside only a few thousands of an inch smaller than the inside of the donut. If you spin the donut with a stepper motor, the ring will resist momentarily and then turn with the donut. Fill the void between the donut and the ring and suddenly you have a viscous damper that will smooth the jerky motion of a stepper motor A viscous damper is very easy to make on a metal lathe. It consists of a weight in the shape of a cylinder with a hole reamed through it. And a case with a hollow "axle" passing through the center. The assembly can be easily manufactured to be assembled with the weight and a viscous oil filling the can prior to the final seal.

The damper is glued onto the worm gear shaft. The damper's size and weight should approximate the motor's diameter and between 25% to 75% of the motor's length. There is a bunch of engineering equations that can be used to make the perfect damper but this formula along with a 0.01" gap for oil and tapped holes in the ends to fill the damper with oil allows tuning by trying different viscosities of oil. Trust me this really works. It kept us safely away from the deep pit of servo technology.   David Orthman   posted by Mel Bartels   6125

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I used 8 fender washers, coated with plasti-dip. That seems to work well. A lot of the noise goes away like it is suppose to. I am not thrilled with the plasti dips appearance after one dunking though. I worry about the balance too. I did plop it in the drill press and spin the thing while the plasti dip was wet.  The washers are 1.5" diam with .25" holes in them. On my dual shafted steppers they help a whole lot at tracking speeds. No neoprene washers in the middle.   Lenord Stage   5259

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Adding flywheels to my set up reduced min delay from 80 to 70. Not much too, but I report it. In my case I use 1.8 volt motors with a 13.5 v supply. That is about 7 times overvoltage.   Jean-Charles Vachon   5219

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so here are the dimensions: 1/4 inch thick, about 2 1/4 inches diameter. They are made of mild steel. But the flywheels should not be considered by themselves...you need to consider the size/angular inertia of your stepper motor rotor. Me steppers are NEMA frame 23 - about 2 1/4 inches square, and about 2 inches deep/long, with a 1/4 inch shaft...this is a fairly common stepper motor size in surplus catalogs such as C&H Sales. If you have larger steppers you may need a larger flywheel, and so on.   Tom Krajci   1359

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The formulae for flywheels is pretty simple and starts with a discussion of inertia requirements for the drive input. But the bottom line for our stepper motors with their tiny inertia, is that any type of flywheel added will be a tremendous improvement. Matching the best flywheel shape (distribution of mass in the flywheel over distance from the shaft center) is an exercise in matching ramping and telescope inertia. But again, unless you have a massive metal instrument, this is hardly worth computing.    Mel Bartels   268n

I suggest making the flywheel several times the mass of the stepper rotor, and placing the mass at a diameter that is several times the worm diameter.  Mel Bartels 278

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+++

...regarding the effects of flywheels: the flywheels add rotational inertia to the motor's rotor. The reason that this helps increase the max speed is because of the way the current ramps up in the motor coils, starting at zero at the beginning of the pulse and ramping up to the steady state value (equal to the voltage applied divided by the DC resistance of the coil) after a certain amount of time; this is due to the inductance of the coil. As the motor speed increases, the length of the pulse decreases, and eventually the pulse is too short to allow the current to ramp up to the steady state value. Since the torque due to the magnetic attraction/repulsion of the coils to the permanent magnets in the motors is roughly proportional to the current through the coils, as the pulse width decreases (average current decreases) the force driving rotation of the motor decreases. The forces opposing the motor turning, such as the permanent magnets forcing the coil to line up on even steps, and friction on the motor bearings don't decrease as the pulse width decreases. So eventually, at high enough speeds (short pulse widths), the forces opposing the motor turning are greater than the forces trying to make it turn and the motor stalls. There is also a force due to the rotational inertia, which trys to make the motor spin at a constant speed, or in other words, resists any change in rotational speed. At high speeds, the rotational inertia helps pull the motor past the humps in the torque required to turn the rotor (you can feel this if you turn the rotor on a motor that's not even hooked up - it takes force to move the coils away from being aligned with the magnets). If you add flywheels (more rotational inertia) that torque getting you over the humps is greater than without, so the motor will not stall with higher speeds (shorter pulses, lower average coil current, less turning torque from the motor).

The key point is the additional rotational inertia makes it harder to change the speed of the motor, so while it makes it harder for the motor to suddenly stop (stall) it also makes it harder for the motor to start, which means you will have to run a bigger maxdelay to start up without stalling. Anything you do to minimize this effect (like letting the flywheels slip on the shaft) will also minimize the desired effect of allowing higher maximum motor speeds. It's a classic tradeoff - the more help you want on the high speed slews, the more you negatively impact the startup. Added flywheels also mean that the max ramp speed will be slower, too, but the biggest speed change is going from zero to whatever when you start up. Hope this helps - I know it's always easier to find what's wrong with what someone is doing than to suggest a better way - in my case I found that increasing the motor voltage and putting series resistors in the line helped my max slew speed more than anything; flywheels didn't help much. I don't think I've got my flywheels real well balanced however, so that may just be my lack of mechanical inclination, not that flywheels don't help significantly.  Steve Rivet   10363

+++

Q.  Weight of the flywheel=100grams (3.5 oz), diameter 39 millimeters (1.53 inch)  How can I arrive at a smooth movement with the flywheel, when the microsteps are already at about equal length?? How can the fullstep be longer now??

A.  Your flywheel is too powerful - remove some mass at the outer edges.   Mel Bartels

+++

.... thing attached to the motor is a Vexta viscous damper. They call it the 'Clean Damper'. It is absolutely amazing how it improves both the slew speed and the smoothness of the start.  I had played around with solid dampers before without noticeable improvement in performance. For me, this one really makes a big difference.   Ben Davies

+++

F+, F-, FQ, FF, FS - that sort of thing            Mel Bartels

+++

Scope.exe controls both field rotation and focuser motors simultaneously.  Confusion arises because the PCB that I sell only controls one of these motors (your choice): you have to supply the controller for the 2nd motor. Mel Bartels 

+++

An example of a simple circuit approach is at http://www.ozitronics.com/data/ucn5804.pdf . Info on the replacement for the hard to find SAA1042 is at http://www.ee.vt.edu/cel/datasheets/mc3479.pdf. Its not a pin for pin replacement, but Mel has info on building a socket that swaps the leads around. An even better approach is one Joe Garlitz put me on to at http://www.oregonvos.net/~jgarlitz/focus_control.htm I am building one of these for my system now, since the counter is a really great way to keep track of previous focus positions when switching filters that are not parfocal, etc. 

My reasoning for suggesting going to a seperate driver from the one on the scope.exe PCB is if you get into photography, you will want to start using capabilities like PEC and autopecsync to get the best performance, and those start taking up parallel port pins. Chuck Shaw

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Typically one uses a MC3479 or a SAA1042 with a small bipolar motor for field rotation and focusing. A small DC motor with two relays will work also for focusing. Look on the above webpage for circuit diagrams relating to these motor chips.  Mel Bartels  11225

+++   F

Nov 14, 2002:   . Added F5/F6 function key focusing control, courtesy Marty Niemi.    Mel Bartels 

+++    F

Not too many stepper driven focuser designs out there - basically add a motor running at 10 rpm onto a typical focuser and it will be about right.    Mel Bartels

+++    F

+++  F

Put the handpad into focus mode. Press the left mode key to activate focusing. The left/right (actually the CCW/CW) direction control buttons will operate the focuser while the up/down direction buttons will continue to operate the telescope. Pressing the right mode key will deactive focus control and return all 4 direction buttons to operating the telescope altazimuth directions.  The speed switch controls the focus speed: if in highspeed setting, you will see FF appear on the screen, and if in slowspeed setting, you will see FS appear, for focus fast and focus slow respectively. Make sure that fast focus and slow focus speeds are set to reasonable values.  Whether the scope is tracking or not has no bearing on operation of the focus motor. Ideally tracking will be turned on for most accurate focusing.    Mel Bartels

+++   F

Added mouse control. Wireless operation at the eyepiece is now possible. A wireless mouse like the gyro-mouse can substitute for both the handpaddle and a motorized focuser controller. Note: these functions subject to change as provision is made for grand tour and scroll functions!!!    Mel Bartels  

+++   F

Feb 1, 04  

+++  F

A.  You want the focuser shaft that the hand knobs attach to to move at 10 rpm.  This is a range of speed that the bipolar stepper will operate nicely at.  So no gear ratio is needed.    Mel Bartels   11394

+++  F

+++ F

(Scope.exe) has the ability to focus via a stepper motor. By placing focusing commands in a scroll file, based on that night's projected drop in temperature, you can compensate for the drop in temperature. In addition, my software will accept LX200 commands so that programs like ACP with higher level scripting can send focus commands, again either projected or computed based on sensor readings. Mel Bartels

+++ F

EPFocusPosition[2].Name Toucam Web Cam     Renato Bonomini     N45°24' - E10°29'

+++  F

Watching this system autofocus is mesmerizing (Marty warned me of this)! I have blown away entire evenings that would have been great for imaging just showing off how this system autofocuses. Then I have also had focusing contests between FocusMax/Scope.exe/MaxImDL and "human" operators manually operating my motorized focuser and watching the CCD images coming in.  FocusMax has never lost, and generally gets the whole job done in about 2 minutes (my focuser is REALLY geared down so the motion is REAL:LY slow).  While focusing with my newtonian has never been difficult (I use the diffraction spikes to get it really sharp, and then look for dim stars to come in and go out to further tweak it) some nights I have spent 30 minutes trying to tweak focus manually with my SCT (even using hartfield masks and also dowells suspened across the corrector plate).......Never again! Chuck Shaw

+++  F / FDR

New variables added to config.dat (see the configuration page for further information on these variables):
[*** focus section ***]
FocusMethod 2
ReverseFocusMotor 0
FocusFastStepsSec 500
FocusSlowStepsSec 100
FocusPosition 200

3. Made a minor change to parallel port pin assignments for auxiliary control and number of mouse clicks to trigger an event for consistency's sake. They now look like:

A motor CW = handpad up = mouse up (1 click) = aux 1 = mouse focus slow plus = LX200 focus out
A motor CCW = handpad down = mouse down (2 clicks) = aux 14 = mouse focus slow minus = LX200 focus in
Z motor CW = handpad CW = mouse right (3 clicks)= aux 16 = mouse focus fast plus = LX200 focus out
Z motor CCW = handpad CCW = mouse left (4 clicks) = aux 17 = mouse focus fast minus = LX200 focus in

handpad CW + MsSpeed = handpad focus slow plus
handpad CCW + MsSpeed = handpad focus slow minus

pport pin 1 = field rotation pulse or focus pulse
pport pin 14 = field rotation direction or focus direction, on = CW = out = plus
pport pin 16 = focus pulse
pport pin 17 = focus direction, on = CW = out = plus

4. Added new display field showing the rate of field rotation in degrees per minute. The 5 fields underneath "FieldRot" are labeled: 'A' for field rotation angle, 'R' for rate of field rotation change, 'M' for field rotation motor angle, 'M' again for field rotation motor step position and reset count, and 'G' for handpad buttons rotated guide angle. Mel Bartels

+++  F / FDR  Hot motor

Q. .. my Field Rotation Motor gets hot, really hot. The driving chips is ok, but I can't understand what is going on with this motor.  The motor is the Applied Motion Products 9.2v .24amp, 200 Steps/Rev.  It is the bipolar one that came with the board I built.  Any ideas as to why this is occurring?     RobertB

A.  A common problem with this type motor and driver. One coil will always be energized because one of the outputs of the driver will always be low on its output pin.  Dave Bevel

A.  Your voltage may be too high for the continuous use of the motor. You can decrease the voltage or limit the current.  Ken Hunter

A.  Running on 12 volts? Yes, motor will become very hot. When motor is 'on' for extended times, important that motor voltage be equal to or above  supply voltage.   Mel Bartels  

A.   slapped a 7809 VR on pin 16 of the FR chip. File (FR_HOT_MOTOR_MOD.jpg http://f5.grp.yahoofs.com/v1/4FFwP61iGU1cQ3kw17Z25l2ouw2ErqhtXmg_SWtmFeryT7gfmfTsw8zaMElHhxWOw1ARNMmvMnXNoWZPWBbgFsSOqzpHW1BuVUXBqw/FR_HOT_MOTOR_MOD.JPG ) is uploaded in Files Section. It worked like a charm. FR chip and motor no longer get hot. Just needed to put a small heatsink on the regulator.  RobertB

A.  You'll also need to put a small Tantalum/electrolytic capacitor on the pin 16 (output of the regulator) to kill any possible oscillations there. Usually a 10 UFD @ 16 volts will do fine.  Ken Hunter

A.  My FR motors also get hot since they stay powered on one winding for a long time. My approach was a bit simpler than adding a regulator though. I just added a ceramic power resistor equal to about 2/3's of the resistence of the motor windings resistance. I added it in series with the power going to the common wire going to the unipolar motor since the way the daughterboard I use is wired, the TIP120's that get controlled by the stepper driver chip simply selectively ground the return lines from each coil.  Since I think your motor was bipolar, you would have needed to add it to the motor power input to the chip (like you did for the 7809).  

I have found that you can drop the voltage to the FR stepper quite a bit and still have plenty of torque available to operate the FR system since the motor is turning so slowly. The only place it can bite you is if you use the ability of scope.exe to slew the FR system, your speed is limited since the voltage is lower than normal going to the motor.   Chuck Shaw  http://www.ghg.net/cshaw/frsys.htm  

+++  F / FR

The traditional SCOPE board keeps the current flowing continuously trough one of the motor coils. In my opinion this solution presents some disadvantages: - Only low currents are possible, resulting in low torque of the motor, hence the need of a consistent mechanical reduction for reaching an adequate torque. In other words, that means also an higher complexity of this device. - Heavy battery consumption;  - Need to provide a switch on the panel of the electronic  box, for disconnecting the focuser and therefore some additional  manual operations for using it. But it doesn't help in case of a field rotator during long exposures....

GEARING :       Molded   Worm Gear   Friction Roller   Roller Slippage    Gear Boxes     Cable drive     Sector     Velcro drive   Bearings  Clutch  Chain Drive

http://www.bbastrodesigns.com/cot/mechanic.html       Plain Bearings               Gear Ratio         

    Molded:   JB Weld-(Epoxy)     Mark Rice    Rex Kindell - 3 rod method

Couplings:  Guardian

+++

Parts Supplers

https://sdp-si.com/index.asp               http://rswww.com/cgi-bin/bv/rswww/subRangeAction.do?cacheID=uknetscape 

+++

...most of the RS Components gearboxes have around 2 degrees of backlash and a undetermined amount of periodic error in the gears.  For that matter so do all gearboxes.   Each time I plan a telescope drive i try to keep to no more than two sets of gear tooth to tooth contact, A primary reduction and then a worm and wheel reduction.

The more tooth to tooth instances you have the more errors can creep in. The RS gearboxes use a lot of pinions to get to 500-1.

Belts have periodic error, present as changing velocities, as do chain drives and for that matter rubber friction wheel drives.

Take your pick but keep the component count as low as you can. My drives work just fine with two pinions and a worm and wheel.    Kevin Gambrell

+++

I've had surprisingly good success with molding large worm gears from simple materials: plywood disk/sector, nylon threaded rod, and JB Weld. Periodic error is plenty good for visual use (20 arcsec peak-to-peak or less) and with care and maybe some lapping this technique may be good enough for some imaging applications. Also, large worm gears allow direct drive...so if your motors don't ever stall...you can get "in the blind" pointing accuracy with Mel's software that is quite good. I'm currently getting 2 arcminutes RMS all sky pointing accuracy...and Mel has yet to implement further correction routines that should bring it down to 1 arcminute.

The future's so bright I gotta wear shades! ;-)    Tom Krajci    7

One hint is if you are using the nylon rod be sure to spray it with something like silicon and for your half circles put some tape at the end of the grooves so the JB doesn't spill out. Also let it dry vertically in a clamp (don't lay it down). I used duct tape to secure the nylon rod with some small bar clamps for the ends of the rods, because the ends tend to flare out.    Mark Schaffroth

Q.  Is there an issue with scope.exe regarding odd vs. even number of teeth in a  worm gear?

A.  Even or odd number of teeth should not matter. Lenord Stage

+++

A.  I have a very similar setup and ran into the same problem with slippage. A quick and dirty fix was to wrap the steel roller with sandpaper. I used the type that plumbers use for cleaning copper tubing for a sweat solder. It's cloth-backed, the abrasive is even and well-bonded, and it comes in a roll around 1-1/4" in width. It's worked so well for me that I've been using it that way for a couple of years.  I glued it to the roller using regular wood glue (it may have been the waterproof style) because I didn't want anything that was too permanent.  The trickiest part was getting a smooth seam. I cut the seam on a diagonal and it rolls quite smoothly.    Dan Wilder

I have tried two solutions. The first is to scrap the rollers on one scope and replace them with gears. While I saw some improvements, inherent problems with the inexpensive gear systems I'm using are evident.  For my other system, a roller reduction/roller drive system, I'm keeping the roller drive. I'm now working on using the high resolution encoders to give the position feedback to counter the pointing errors. Brad Davy

A.  The RS gearhead output shaft is indeed 8mm. I have a machinist make up couplers that have an 8mm bore on one end and .25" bore on the other end. They are 1" long. Don't bother trying to DIY this unless you have a lathe. The centers of each hole have to be perfect.  As for the stepper to gearhead, there is a pinion or adapter kit you buy when you buy the gearhead. The little pinion fits on the stepper shaft with Epoxy. You then insert it into the gearhead.  The pinion kit gives you two (gears). One is .250 and one is a little smaller. They label them 6mm and 6.25mm.  This pinion fists directly onto the stepper shaft. They look like tiny spur gears.  (I saved all the ones that are smaller and had the machinist bore them out to .250" for me. Free pinions!)    Lenord Stage

A.  I'm making my own pillow blocks, so I  just ordered some 8mm shaft and bearings and connected the 8mm shaft back to the gearbox with 5/16" fuel line.    Ben Davies

The answer is not to use grooves at all and let the cables walk up and down the capstan!  See http://mysite.verizon.net/res0owmd/id4.html  The driving pulley or capstan is smooth and parallel with no grooves at all. There is no change in diving rate as the cables walk up and down.  Don Clement

CHAIN DRIVE:

     Bearings       McMaster/Carr    BigBearings    VXB

   CLUTCH 

A.  Best material I have found thru the years against aluminum gears is masonite. Tough, and when its coated with a very light coating of light weight grease (like fishing reel grease) it provides a nice smooth clutch.  Chuck Shaw

GEAR RATIO:http://www.bbastrodesigns.com/operate_fullstep_sizes.html 

# of microsteps should be based on 2 factors: use sufficient microsteps such that an individual microstep is 1/4 to 1/2 arcsecond in size, and, sufficient microsteps such that the motor feels smooth when tracking.   Mel Bartels

+++

If you divide the Arcsec per Fullstep by the number of microsteps, you will calculate the size of the microstep in arcsec. Again in my example it would be 1.2 arcsec per fullstep / 4 (I'm using 4 microsteps for the G11 mount) = .3 arcsec per microstep.   Don D'Egidio

+++

My software supports 40 microsteps per fullstep, so I recommend drive ratios of 500:1 to 1000:1. If the drive is smooth and modestly dampened, there is no reason anymore to go above 1000:1.   Mel Bartels

+++

The reverse motor option in config.dat is for handling cases where the location of the motor with respect to the gearing causes the motor to move in the wrong direction.Mel Bartels

+++  

Mel’s reduction design (and mine) were done when the software only supported 10 microsteps. Now that 40 are available, an overall ratio of 625:1 will produce 1/4 arcsecond steps. A lot of us (me included) can't get 40 microsteps working evenly with our computer/motor configuration, so must live with somewhat higher reduction ratios.   Tom Alexander

+++  

I have gone down to 720:1 with 40 ms and do just fine. This is only on a 10" dob and a 6" Mak-Cass mind you. Visually, 720:1 is great with 40 ms/step to at least 400x, confirmed.  Lenord Stage

+++

I built my 20 inch scope back when 10 microsteps per fullstep was the maximum the software could do. Now it's 40 microsteps per fullstep, so the 2000:1 can be cut by a factor of 4. In addition, people running at 359:1 report good results at high power.   Mel Bartels

+++  

Q. any thoughts on what the resolution for the declination axis could be?  In the end I will use a ccd on this (equatorial) telescope.

A. The declination can be quite coarse, down to 200:1 or so.    Mel Bartels

+++

So the point of the 40 microsteps, if you care to tune them, is to allow down to 359:1 gearing with a bolt on stepper motor of 200 steps per revolution. The 359:1 being a popular gearing, it makes adapting the common equatorial mount to a motor control easier since you don't need a gearhead on the stepper. Not everyone needs the 40 microsteps, of course.   Mel Bartels

+++

Q.  Where can I buy a book or something where learn how to build a drive system???

A.  Microcomputer Control of Telescopes by Genet and Trueblood is the bible. Mel Bartels

+++

...my system started with 10, then 20, and very recently 40 microsteps per fullstep. 10 years ago, back when I had my initial 'mature' versions doing 10 microsteps per fullstep, this was considered quite the feat, now, it's rather lame. However, this has meant that historically, most people have made their gearing about 2,000:1.

So I would encourage people to start thinking about faster gearing of 300:1 to 500:1, instead of the traditional 2000:1 (my 20" system, now 6 yrs old, with Byers gears, is about 2500:1). This will gain you 4x to 5x speed with no loss in smooth tracking if you go to the 40 microsteps per fullstep.

Yes, I have plans to go to 256 microsteps in the future. This could mean 0.2 arcsecond microsteps with 20 deg/sec slewing, using reductions of 50:1 (say, stepper driving drive shaft of typical roller drive directly with no intervening reducer).

+++

the only consequences of too big of a gear ratio is slower slew speed and slower max microstep speed, which can mean a bigger hole at the zenith that is not trackable through, so this is not an issue unless these consequences mean a great deal to you        Mel Bartels

+++

...several astrophotography books recommend controlling the scope to at least twice the max resolution of your scope. I think this has to do with effects of scope vibration/overshoot and other dynamic effects on long exposure photography, but haven't spent the time to think through why this would be true.

The Dawes' resolution equation is: sep"=4.56/Diameter of scope in inches. As Marti said, the max resolution of the 16 inch diameter scope is 0.285 arcsec. So, an ideal astrophotography system (according to my references) would have tracking accuracy of better than 0.1425 arcsec  Larry Bell 8922

+++

With the JB Weld worm gears the azimuth step size is trivial to determine...count the number of teeth in the gear  Tom Krajci 3097

+++

Q. Now if I only knew how many teeth I actually made on the gear.. I know its somewhere between 698 - 702, I sure hope I don't have to count them!

A.  The software can help in that regard. You can command a move of X halfsteps...assuming 400 halfsteps per motor rotation, and 698 teeth you
need to move 279,200 halfsteps to make a complete rotation of the scope Then it's easy to see if you ended up exactly at the start point, or a couple teeth short or long....  Tom Krajci       PS. As a gut check, make note of the motor shaft orientation at the beginning of this long slew...the shaft should be in the same orientation at the end...then you are sure you did not lose any steps along the way.

+++

Last night I was experimenting with refining the stepsizes I am using in Config.dat. My motivation has been that I have always seemed to have a small amount of Az drift present after starting tracking, no matter how carefully I do an init sequence...... I have done a spin align on the scope to get the mechanical alignment very close, so the Z1, Z2, and Z3errors are quite small.

The tapered roller for Az is very difficult to measure for the roller reduction accurately enough for my stepsize (my stepsizes are only about 1.5 arcsec, so tiny errors really show up as rate and slew errors!). Mel's recent addition of having scope.exe use the encoders to calculate stepsize is superb, but suffers from the +/- errors due to the "relatively" large count size in the encoders. My Az encoder is 8602 counts/360 deg (an 8192 encoder driven by gears in the ratio of 126:120 teeth). The count size is over 150 arcsec/count, which is 100 full steps, and 1000 microsteps!!

Even when using the 1/2 step option to move a specified number of 1/2 steps, and commanding 350,000 half steps (to have the count +/- error be a small part of the error sources), the answers that scope.exe would provide would still vary quite a bit, depending on the encoder counts and where the mount was in reading them. For a mount with 5 or so arcsec/step, this is not a problem, but for us "tiny step" folks, the stepsize needs to be more accurate.....     Chuck Shaw  82

+++

+++

To adjust gear ratio when slewing:  If slews are short, decrease FullStepSizeArcsec, if slews are long, increase it.  Ben Davies

+++

GEM FLIP:              http://www.bbastrodesigns.com/operate_gemflip.html 

This section compiled by Larry Bell

NOTE:  The GEM flip functionality has been greatly improved in various versions of Scope since Feb 8 2002.  If you are having difficulty with GEM Flip, check Mel’s web site and ensure you have the latest version of Scope.exe.  As a result of these improvements, the majority of the comments in the database from before Feb 2002 are no longer applicable.   Larry Bell

+++

Cut to the chase.  Just tell me step by step how to do a manual GEM Flip.

+++

11/24/04    Added new config variable: GEMFlipPossible, which controls whether the GEM meridian flip can occur at all. Before, GEMFlip possible set from  initialization state equal to equatorial. This allows GEM flip to be possible with user defined initialization state. If AutoGEMFlip is set to true, then GEMFlipPossible will also be set to true.  Mel Bartels

11/26/04 For my northern location:

In config.dat, latitude = +42.7 for New Hampshire
Start up with declination arm horizontal with scope on east side of
pier pointing at celestial equator.
Start up with option 1.
Start up with Alt/Az = 0/0.
On startup, Dec = 0, Ra = local sidereal time = 1:50 at 9pm local time
GEMFlip state OFF.
Select Alp Ori and hotkey '1'
Scope requests slew of 173 degrees.
Scope then slews to target rising in east with tube slightly above
celestial equator. GEM flip state changed to ON.
Select M42.
Scope moves down (south) ~13 degrees.

For "southern" location:

Assume top of polar axis now pointing to south celestial pole.
Start up with declination arm horizontal and scope now on
opposite side of pier, (still east side)
In config.dat, latitude = -42.7 This puts me somewhere near
the Chile/Argentina border.
Reverse direction of Alt/Dec motor.
On startup, everything displays as before.
Select Alp Ori and hotkey '1'
Scope requests slew of 187 degrees.
Scope then slews to target rising in east with tube slightly below
celestial equator.
Select M42
Scope moves down (south) 13 degrees.               Don Ware

+++

Nov 14, 2002:     Added hotkey for gem meridian flip: either '[' or '{'.    Mel Bartels

+++

If you have good polar alignment, do not redo the inits. Just do the reset to equatorial. If you start W->E, then you should do the GEM flip in software, followed by 'reset to equat', to get the scope software oriented properly.  Without it, you will get what you describe next.     Mel Bartels

"When tracking turned on, the scope would go nuts trying to slew, with immediate GEM aborts. If I did not do the reset GEM, the scope would not slew, but still had major tracking errors"

Whenever you get into a situation where tracking and goto are very bad and resets happening all over the place, then the inits and scope position (ie polar alignment  -  bd) are bad. Kill the inits with the 'k' key,  manually enter altitude and azimuth values (eyeballing is good enough to get going), and try the init sequence again    Mel Bartels            #10245

+++

If you kill the inits, then until you do both inits, the reset to equatorial coordinates will not do much.                          Mel Bartels #8584

+++

Q.   After doing a polar alignment does it matter what the GEM flip display setting is (E->W or W->E) when initializing on a star, or is it only relevant when making the flip?

A.  Don't initialize after setting up for equatorial mount, but instead, pick equatorial option at startup time. From then on, do a reset to equatorial coordinates when you wish to synchronize scope to sky.  

If you wish to do initializations, always do them on one side of the meridian --- don't mix them across the meridian IF that means a meridian flip. Mel Bartels9867

+++

Q.  When does the Auto GEM flip occur?  During GOTO activity or just racking? I have AUTO GEM FLIP turned on, yet when I GOTO from the east to west or west to east the mount just slews instead of flipping the mount.

A.  Both, in the later versions of scope.exe    Mel Bartels 10093

+++

Q.  Even with the auto flip turned off (0) it still wants to move both axis when I try to HS past the meridian.  Any ideas? This is the Jan 2002 version BTW.

A.  in config.dat, set the AutoGEMFlipFuzzDeg to 180    Mel Bartels 9071

+++

Q.  By the way, how do you abort a GEM flip? Once started, I hit esc, but the program refused to give up and continued to try to flip the scope. L. Bell, #8582

A. You gotta turn off tracking, so keep hitting the 't' key until all the slews are aborted and tracking is off. Mel Bartels #8584

+++

If declination moves opposite from what you expect, then scope.exe and the telescope disagree on status of GEM flip. Do the GEM flip once, and a reset to equat, and all should be ok. Mel Bartels, #8574

+++

Q. I just spent a very frustrating evening in the cold trying to check out my new mount's operation and had continual problems with the GEM flip. I followed the advice given by the folks in this thread, but the scope still takes off when I think it shouldn't (and doesn't need to do a GEM flip) and goes in the wrong direction. Larry Bell, #8582

A. That's because I have been giving out the WRONG advice! In checking the code, the scope actually moves clockwise when moving into a flipped state. So start the scope on the east side aimed westwardly. The scope's RA will be less than the sidereal time. It is important that you verify RA vs sidereal time, as a simple 'reset to equat' does nothing to fix any sidereal time errors (which would be caused by bad computer date/time, longitude entry in config.dat, timezone entry, and so forth) and consequently does not fix any hour angle errors (how much you are east or west of the local meridian). It is the hour angle that the meridianflip is based on. I've also added a query for meridian flip direction - hopefully that will help. #8584

+++

Q. I've got a problem that when I turn on Scope and try to slew the telescope to a star for resetting on, the programs decides I have to do a GEM Flip and takes off on it's own. I can abort the slews but it keeps trying to do it, turning off tracking each time.  Is the process (on a GEM) start up scope...enter a star from a datafile...slew to the star...reset to equat? Is this where I'm going wrong? I'm trying to move to the star before I select one. I've got encoders on the system and have The Sky program working thru the LX200 interface but I can't get started for these slews.  Lenny. #8491

NOTE:  Newer versions of Scope have a GEM flip indicator to show that GEM flip has occurred.  Also, an indicator is included to show which side of the pier the scope is on.  Mel Bartels, #8503

 … another way to see if the gem flip has occurred, is to compare altitude and declination values. If different, then it has occurred. If same, then no gem flip has occurred (or an even count of them has!).  

If the scope is very lost to start with, then slewing to a star may cause the gem flip to be activated. Compare the hemisphere the scope is pointed at with the side of the mount the scope is actually on. For instance, starting on the west side of the pier should mean that the scope is pointing at something in the eastern sky (RA is greater than sidereal time). Do a reset to equat of any star in the east, or even enter a faked RA that is approximately correct (based on gazing at the mount from a few feet, is the scope pointed 1 or 2 or 3 or ??? hours east of the meridian?)

The DST is set to the value of daylight savings time, which in the USA, is zero now. It won't affect things if you do a reset to a star, as the incorrect DST will be compensated for. However, if you rely totally on geographic coordinates to get started, then it matters, as incorrect DST affects what scope.exe thinks is sidereal time, or, the current right ascension value at the meridian.  Mel Bartels, #8499

+++

Can anyone describe for me the Alt/Az reference frame for a GEM scope? What is 0 Alt, 90 deg Alt, 0 deg Az 90deg Az etc as measured from the polar axis?

…equatorial telescope: altitude is same as declination, azimuth same as hour angle (degrees east/west of meridian) however, when you do the gem meridian flip

declination is now mapped to altitude so that
dec = 90 = alt = 90
dec = 45 = alt = 135
dec = 0 = alt = 180
dec =-45 = alt = 225(notice how dec now travels in reverse compared to altitude) and azimuth is mapped to hour angle with  displacement of 180 deg  Mel Bartels #8819

+++

Q  Does the software take care of the GEM flip orientation when your latitude is negative (pointing to the SCP), ie has the program taken into account that the E and W directions are reversed in the southern hemisphere?

A.  You want to start on the side of the meridian where the declination and altitude both agree and change together. That should be east side facing western hemisphere.  el Bartels9867

The E and W directions are not reversed in scope.exe when in southern hemisphere. However, scope.exe does concern itself with motors that move the scope in clockwise and counterclockwise direction. These directions are based on you standing with your head to the top of the azimuth axis with increasing azimuth as you rotate clockwise. This direction as it is mapped onto the sky is reversed in the southern hemisphere: in the north increasing azimuth means clockwise means decreasing right ascension, and in the south, increasing azimuth means clockwise means *increasing* right ascension. Note that tracking direction in both north and south hemispheres heads towards smaller right ascension and is clockwise in northern hemisphere and counterclockwise in southern hemisphere.

Perhaps I should add a new handpad mode, called equatorial mode, so that the 4 direction buttons operate the scope N S E W as opposed to the up down clockwise counterclockwise control now. Mel Bartels9867

+++

Q. I've got a problem that when I turn on Scope and try to slew the telescope to a star for resetting on, the programs decides I have to do a GEM Flip and takes off on it's own. I can abort the slews but it keeps trying to do it, turning off tracking each time.  Is the process (on a GEM) start up scope...enter a star from a datafile...slew to the star...reset to equat? Is this where I'm going wrong? I'm trying to move to the star before I select one. I've got encoders on the system and have The Sky program working thru the LX200 interface but I can't get started for these slews.  Lenny. #8491  

A. NOTE:  Newer versions of Scope have a GEM flip indicator to show that GEM flip has occurred.  Also, an indicator is included to show which side of the pier the scope is on.  Mel Bartels, #8503

… another way to see if the gem flip has occurred, is to compare altitude and declination values. If different, then it has occurred. If same, then no gem flip has occurred (or an even count of them has!).

If the scope is very lost to start with, then slewing to a star may cause the gem flip to be activated. Compare the hemisphere the scope is pointed at with the side of the mount the scope is actually on. For instance, starting on the west side of the pier should mean that the scope is pointing at something in the eastern sky (RA is greater than sidereal time). Do a reset to equat of any star in the east, or even enter a faked RA that is approximately correct (based on gazing at the mount from a few feet, is the scope pointed 1 or 2 or 3 or ??? hours east of the meridian?).

The DST is set to the value of daylight savings time, which in the USA, is zero now. It won't affect things if you do a reset to a star, as the incorrect DST will be compensated for. However, if you rely totally on geographic coordinates to get started, then it matters, as incorrect DST affects what scope.exe thinks is sidereal time, or, the current right ascension value at the meridian.  Mel Bartels, #8499  

+++

Q  Does the software take care of the GEM flip orientation when your latitude is negative (pointing to the SCP), ie has the program taken into account that the E and W directions are reversed in the southern hemisphere?

A.  You want to start on the side of the meridian where the declination and altitude both agree and change together. That should be east side facing western hemisphere.

The E and W directions are not reversed in scope.exe when in southern hemisphere. However, scope.exe does concern itself with motors that move the scope in clockwise and counterclockwise direction. These directions are based on you standing with your head to the top of the azimuth axis with increasing azimuth as you rotate clockwise. This direction as it is mapped onto the sky is reversed in the southern hemisphere: in the north increasing azimuth means clockwise means decreasing right ascension, and in the south, increasing azimuth means clockwise means *increasing* right ascension. Note that tracking direction in both north and south hemispheres heads towards smaller right ascension and is clockwise in northern hemisphere and counterclockwise in southern hemisphere.

Perhaps I should add a new handpad mode, called equatorial mode, so that the 4 direction buttons operate the scope N S E W as opposed to the up down clockwise counterclockwise control now. Mel Bartels 9867

+++  

GEMFlip Instructions   6/20/02

From Mel Bartels - Meridian Flip by Bill Wiegert

 The Meridian is an imaginary line (directly overhead) that extends between the North and South Celestial Poles. It "divides" the sky into two distinct halves - East and West. As you look up at Polaris, and then directly south, you will see which constellations are east and west of this imaginary line.  During polar alignment, this orientation should become evident.

 When using any German Equatorial Mount as a motorized GOTO device, objects can be viewed on one side of the Meridian at a time. To view objects on the other side of the Meridian you must execute what's called a "Meridian Flip" (sometimes referred to as a "GEM-Flip"). If this maneuver isn't done, the system will confuse directional movement with the opposite side of the Meridian, and GOTO functions will not be possible.

 Your system was preset at the factory to begin slewing to objects that are West of the Meridian. This is because objects in the west are setting, while those in the east are rising, and western setting objects are usually what observers want to catch first (you have more time to catch those rising in the east).

 The procedure for executing a Meridian Flip is NOT DIFFICULT. In fact, the program does almost all of it FOR you. You merely have to type a HOT-KEY, and then follow a simple instruction on the screen.

 The following procedure will accurately reset the system, to enable pointing, finding, and tracking to be accurate and repeatable on the other side of the Meridian.

 The procedure is performed during an observing session, when it is desired to GOTO and view objects on the opposite side of the Meridian.

   1.. Aim the telescope at a point near the current side of the Meridian, preferably to the North, and slightly to the side of Polaris that you'd been observing on.  (Tracking is off.)

   2.. Type the HOT-KEY ' r '.

   3.. This highlights the RESET function in the program menu.

   4.. Use the UP or DOWN arrow keys to highlight GEM FLIP. Hit <enter>

   5.. A window will pop up: "Now flip the scope across the Meridian; press any key to continue".

   6.. Manually move the telescope past Polaris, across the Meridian.

   7.. Hit a key - Spacebar, ENTER, etc. (The normal program screen returns).

   8.. Aim the scope at a known bright star on that side of the Meridian. Center it in the eyepiece as you did for initial alignment.

   9.. Type the HOT-KEY ' d '.

   10.. Search the Data File for that star. Type its line-letter.

   11.. Type the HOT-KEY  ' t '. Tracking turns on.

   12.. Meridian Flip is complete! You are again ready to GOTO any object.

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GUIDING:

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When microstepping using the handpaddle, only one motor at a time will operate.  Thus the RA motor will stop if you move the scope using the handpaddle in microstepping mode in Declination.

However, if you put the software handpaddle mode to 'guide', then your handpaddle button presses are treated as 'guiding', that is, they are added or subtracted from the basic rate. If you guide in Dec while tracking, the RA motor will continue to track.  Mel Bartels

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Q.  In my experimenting with the guiding mode, I have accidentally updated the drift settings creating some confusing moments on my part when the tracking and GOTO seemed to have gone haywire. 

A.  Turn off the drift update via a menu option. Then pick any guide mode (I like either guide+save or guide+stay+save). Depends if you wish the guide star to remain in position when guiding is finished, or, if you wish the guide star to return to where it would have been if you had done no tracking. The latter is useful for graphically illustrating how much drift is required. It usually isn't much. Use the left mode key to start the mode and the right mode key to end the mode. This works for all handpad modes. You first place the handpad in the mode, then activate the mode as you see fit. That way you can jump between control of the scope with the mode off and control of the mode with the mode on. The modes are detailed at http://www.bbastrodesigns.com/operate_handpad.html .    Mel Bartels 10532

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Guide + stay leaves the guide star as is when guiding is finished.  Guide along by itself will return the guide star to where it would have otherwise have ended up without guiding. This can show you the extent of the drifting during the guiding operation. In your situation, you want the target to remain centered, so use guide + stay.    Mel Bartels 

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All Guidemodes operate in a similar way....

When tracking is active, 1st left button/switch enters the guide mode. A  second left button/switch starts recording the guiding commands till 3 worm cycles are completed or a right mode switch/button is performed. (Only do the 2nd left mode switch when recording  commands to build a periodic error correction file.)

Exit Guide Mode with a right mode switch/button.. If you were recording, the 1st right mode switch stops recording, so to exit guide mode requires a 2nd right mode switch.

When mode is active, buttons move scope at guide speed (GS) while tracking continues at same time.

If Drift update is active, the guiding commands are remembered, and when the mode is exited, the sum of the commands is applied to the tracking rate to "correct" it for whatever drift rate had been corrected via the guiding commands. You will see the rates that are being added to the tracking rates on the main display beside the words "drift". You have to go to the reset
menu to zero out the drift rates.


Guide Mode and Guide+stay mode operate exactly the same as each other when the mode is active. Guide+stay mode maintains the exact position the telecope is at when the mode is exited. Guide mode jumps to where the telescope would have been if the guiding commands had not been sent when the mode is exited. This allows you to see just how much drift had accumulated that you had corrected.

Guide+Stay+Rotate mode operates just like Guide+Stay mode, EXCEPT, the commands in each axis are blended into the other axis as the field rotates.  This is only used for an alt/az mount that is using a rotating autoguider.  It is not used for an equatorial mount.   Chuck Shaw

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GO TO:

First ‘goto’ equatorial mount:

Assuming good polar alignment and good fullstep size numbers in config.dat

Your First Equatorial Initialization and Goto Run: create a scroll file called startup.scr composed of these commands:

trackon
data_file bstars.dat
reset_equat
move_file messier.dat
prompt finished

the first command turns on tracking
the second command says to find an object from the bright star data file
the third command says to reset the telescope's position to the object's position
the fourth command says to move to a Messier object
and the last command displays a 'finished' statement indicating that the scroll file has finished

run scope.exe with the following command

scope -x startup.scr

this says to run scope and execute the scroll file startup.scr

answer 1. adopt an equatorial alignment and turn on the power supply to the motors when instructed

start the scroll file by pressing the left mode key on the handpad or the 'B' key on the keyboard as you do so, tracking will start move onto the next scroll command via the left mode key or the '<' key on the keyboard which loads and displays the bstars.dat file, where you pick a nearby bright star

now center the telescope on the star using the handpad slew and microstepping speed switch and the four direction buttons after centering, move onto the next scroll command via the left mode key or the '<' key on the keyboard which  resets the telescope's coordinates to the star's coordinates now move onto the next scroll command using handpad or keyboard, and  select an object from the messier.dat file; the scope will slew to it finish by moving on to the last scroll command which displays the finish command exit the scroll function by pressing any key    Mel Bartels

HALFSTEP:                   http://www.bbastrodesigns.com/operate_fullstep_sizes.html                           http://www.bbastrodesigns.com/operate_halfstep_config.html 

Micro-stepping and Half Stepping are two entirely different events, controlled separately by the software.  ie MSParams will have no effect on HSParams and vice-versa.

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If microstepping, then speed is controlled by the MsArcsecSec value. Halfstepping is controlled using MinDelay (fastest speed), MaxDelay (slowest speed), and HsDelayX.   MinDelay controls the minimum delay between steps, hence, the fastest speed.   MaxDelay controls the maximum delay between steps, hence, the slowest speed        Mel Bartels

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if you input 999 halfsteps, the software actually moves 1000 halfsteps to keep total control of the motor's rotor positioning.  Mel Bartels    9536

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while DEC does not stall at all - simply because it will never get into max speed with my low gear ratio! It reaches just a fraction of RA speed and has to slow down - it is half way at that time.  Michal

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..........you can't have 2 HS mindelay settings.  Lenord Stage

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HsRampX is ramping time - make this a small number if you aren't getting to max speed quick enough.    Mel Bartels  5966

the equation basically boils down to a square relationship. That is, if you double the ramp up/down time, you can handle four times the torque (or roughly, four times the weight of the tube assembly).     Mel Bartels   493

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Halfstep move is always one motor at a time, while a slew to position will almost always activate both motors at once.  Mel Bartels

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if using interrupt method of timing slewing (DOS):  to get speed, take MinDelay and divide it into 1,000,000 to get halfsteps/second for example, a MinDelay of 100 means a speed of 10,000 halfsteps per second if 200 fullsteps per motor revolution, then motor shaft rotating at 10,000/400 = 25 rev per second over one minute, speed is 25*60=1500 rpm    Mel Bartels

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MaxDelay, MinDelay, HsDelayX: these set the slowest and fastest slew speeds:

When using IRQ 8 timing of halfsteps (DOS), ramp speed starts at (MaxDelay - MinDelay) and achieves highest speed of MinDelay

When using delay loop timing of halfsteps (Windows) with interrupts disabled, ramp speed starts at (MaxDelay - MinDelay)* HsDelayX and achieves highest speed of MinDelay * HsDelayX, where HsDelayX is used as a multiplier to keep the MaxDelay and MinDelay values reasonably sized on fast CPUs         Mel Bartels  3724

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I need confirmation of what I think should be the equivalent of half step tacking. If I set three microsteps with the following PWM values, 100 0, 100 100, 0 100 should this be equivalent to half stepping? -Marty Nemi

Yes. Technically you are micostepping with 2 microsteps per fullstep. Mel Bartels

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Formula to calculate halfsteps per second: 1,193,181 / MinDelay                                   Mel Bartels

To disable microstepping, do not turn on tracking, and leave the handpad in halfstep mode. Mel Bartels

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Tuning the HalfStep Parameters

Q  Could we go over again how to adjust the halfsteps for max speed. .

A.  Simple..... Lower the MinDelay setting till the motors buzz when they are up to speed (assuming you are using (DOS and) the IRQ timing option in  Config.dat).  Lower is faster.

Adjust the MaxDelay to get the startup speed to where you like it without buzzing.....remember to back off the numbers when you DO get the motors to buzz..... I use Min delay of 550 (I get buzzing at less than about 450) and I use a MaxDelay of 2000. The startup speed is Max minus Min, or 1450 for me.... Having a FAST slew speed (MinDelay), and too high of a MaxDelay setting will cause the startup speed to be too fast and can momentarily stall your motors (buzzing sound), or cause some slippage.....    Chuck Shaw 140

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1. Get into the HsParms menu and set MaxDelay and MinDelay to fairly low numbers such as 500 and 100.
2. Using the handpad slew the motor, you will probably find that the motor will not start but just sit there vibrating away.
3. Gradually increase MaxDelay until you find that the motor starts reliably. A MaxDelay below 2000 is quite respectable for 1.8 deg step motors.
4. You now will probably find that the motor will stall as it nears max speed.
5. Gradually increase MinDelay until you find that the motor no longer stalls before reaching max speed. A MinDelay below 700 is quite respectable for 1.8 deg step motors.
6. You can then reduce the rampup speed, HsRampX, to the lowest possible without stalling the motor.    http://www.spin.net.au/~afmartyn/software.html

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The first thing to do is calculate the full step size for altitude and azimuth. For a totally geared drive this is just a matter of making the calculation using the known gear sizes and the number of motor steps per revolution. For a roller drive system like mine you can work out the approximate step size and then take measurements to get it exactly right.

After you have the approximate step size you can adjust the slew speed parameters. Start with large values of MaxDelay, MinDelay and HsDelayX. Gradually decrease MaxDelay until the motor will not start and then increase it slightly so that the motor starts reliably. Next gradually decrease MinDelay until the motor stalls when ramping up to max speed and then increase it slightly so that the motor reaches max speed without stalling. Now decrease HsDelayX to a value that also doesn't stall the motor. I ended up with values of MaxDelay = 1900, MinDelay = 650, and HsDelayX = 1. I also use the S-style ramp. This gave me a slew speed of about 1.5 deg per second and a ramp time of about 5 seconds  Andy Martyn   

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Q. What is the reason for half step slewing vs. full step slewing? I could be naive, but it seems to me the slew speed would be twice the speed at full stepping because there is a physical limit to how many pulses can be sent along the single pin of the parallel port per second?  

A. The speed limit of the parallel port is magnitudes faster than any stepper motor could ever accept pulse inputs. The halfstep slewing has more torque than fullstep slewing and less cogging/resonance effects while ramping. That's because two windings are occasionally on vs only one winding on at a time.   Mel Bartels

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Q  I have no torque when i set my min delay below 350!

A  That's not a bad rate - you are at roughly 3000 halfsteps per second.

You should be able to double up to quadruple that rate if you employ an overvoltage power supply, or use one of the other tools like flywheels.      Mel Bartels  8014

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You might try making the maxdelay 1500, hsramp 6 and MinDelay 800. If the motors will move ok at these speeds, and not stall, decrease the larger values by 50 at a time until the motor stalls, then add 50 back in and go to the other value.  Lenord Stage

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Ramp style of 1 with the 'S' shape curve means that it starts slower, ramps quickly in middle speeds, then tapers off slowly before reaching max slew speed. Depending on settings of other variables, you may not see much of an effect.     Mel Bartels 5967

+++  this is not from scope-drive list:(below)

In the motion-control industry, "profile" describes a complete and controlled motion event. That is, the move accelerating from a base velocity to a slew or run velocity, continuing at the slew velocity to a designated deceleration point, and then decelerating back to the base velocity.

Base velocity doesn't have to start at zero. A profile can begin from any previously established velocity V1 and be considered complete at any other velocity.

In a trapezoidal profile, the acceleration and deceleration rates of a motion are constant, as you see in Figure 2a. The velocity accelerates linearly until the profile reaches the required slew velocity. During deceleration, velocity decreases linearly until motion reaches its target velocity (Vx).

By contrast, an S-curve profile is a controlled velocity (or ramped acceleration) profile. As Figure 2b shows, the S curve is more complex than a trapezoid since it's based on two linear incrementing or decrementing variables over time.

A trapezoidal profile applies only half as much torque loading as the S profile does at halfway up the velocity profile in the same time frame. However, the S curve generates a softer move at the profile's leading and trailing ends, thus lowering impulse torque loading (i.e., jerk).

To gain these advantages, carefully match the update timing for the S acceleration profile to system dynamics.

Medium-to-high inertial systems, noncounterbalanced vertical systems, or other similarly imbalanced systems may defeat S curve's ability to perform. Gain structures can be implemented to overcome this deficiency.

Using only a PID gain structure without any other form of gain assistance, the S curve may not perform any better than the trapezoidal when placed in a high-friction environment (above a 0.15 coefficient). The same holds true when operating in a medium-friction environment (0.075-0.15) and applying a current motor operation without tachometer feedback.

Interestingly, to achieve the same acceleration time versus distance, the peak acceleration achieved at the S's crossover is twice that of a trapezoid. 

this is not from scope-drive list:(above)

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MoveHsMsgDeg  Degrees of halfstep moves before message appears asking for confirmation of move

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Q.  Every time I slew more than about 10 deg the software stops and asks for confirmation before proceeding with the slew.  Is there a setting in config.dat where I can disable this feature?

A.   Yes, in the [*** display section ***] there is MoveHsMsgDeg 10.000000

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Q.  The really annoying thing was that I could hear the motors ramping up but there was no actual movement of the rotors.

HANDPAD: 

http://www.bbastrodesigns.com/cot/operate_handpad.html    http://www.bbastrodesigns.com/handpad-assembly_notes.html  

Dave Bevel's handpad diagram             Annotated Handpad            Handpad.gif   Mel's circuit drawing 

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Use the left mode key to start the mode and the right mode key to end the mode. This works for all handpad modes. You first place the handpad in the mode, then activate the mode as you see fit. That way you can jump between control of the scope with the mode off and control of the mode with the mode on. Mel Bartels 10533

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When a handpad direction button is pressed in altaz control mode (as opposed to guide mode), the altitude or azimuth is commanded to move and the scope then accumulates altitude or azimuth until the handpad button is released. At this point new equatorial coordinates are calculated and if tracking is on, tracking resumes using these new equatorial coordinates.

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use the speed switch in the middle of the handpaddle to jump between micro and halfstep    Mel Bartels

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Scope.exe checks the handpad at startup to see if it is giving sensible readings. If not, it is disabled.  Mel Bartels

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You can use the hotkeys of F1-F4 to simulate the handpaddle buttons for microstepping motion.  The F1/F2/F3/F4 keys actually do microstepping.   Mel Bartels

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Do this with menu selection:   motors | auto adjust ms parms set pwm for 30 or 40, and current at 100% (assuming 12 volt supply and 12 volt motors, if 6 volt motors (and 12v supply), then set current at 50%); let run for a few seconds to stabilize now hit the f1 or f3 keys and see if the motor turns in microstepping mode go into menu selection   move | halfsteps   entering 400 steps - see if motor spins   Mel Bartels

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handpad configuration variable called HandpadDesign. It can be either StandardHandPad (value of 0) or DirectionOnlyHandPad (value of 1). If  directionOnlyHandPad, more than one direction line can be active at a time, allowing for guiding motions in two axes simultaneously. The 4 motion direction input data lines should be hooked up as follows:

upper button = Up, activates bit 16 or pin 13 of the parallel port
lower button = Down, activates bit 32 or pin 12 of the parallel port
left button = CCW, activates bit 64 or pin 10 of the parallel port
right button = CW, activates bit 128 or pin 11 of the parallel port

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...when you say "I press one of the guide correction buttons on the hand paddle", you actually mean that you are simply pressing one of the direction buttons, and the scope either microsteps or halfsteps based on the speed switch?

If so, that is correct. If you want true "guiding", put the handpad into one of the guide modes. Then the direction buttons become equatorial north, south, east, or west, and both motors will track if necessary.
 
The difference is that in the first case mentioned, the buttons simply move the scope, one direction at a time. In the second case mentioned, the buttons act as guiding corrections in the sense of + or - RA or Dec. Mel Bartels

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Trouble shooting the handpad - I would try running the parallel port test and see if any of the handpad,(10,11,12,13), pins are active

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for all the handpaddle guide modes: left mode key starts, right mode key ends     Mel Bartels

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Q.  is there a way to "reset to equatorial coordinates" via the handpad? Sure would be handy. Larry Bell

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added control option to flip the north south buttons on the hand paddle; this will help those who have to do german equatorial mount meridian flips and others with reversed views    Mel Bartels
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Added new menu options under the handpad section to simulate the mode switch flip to the left and to the right. Now you can activate whatever function you wish, such as an analysis point, or turn on/off guiding, based on the handpad mode that you are in, without recourse to the handpad.   Mel Bartels

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For smooth corrective action with the handpad while tracking, put the handpad into guide mode and allow it to add/subtract to the scope's position to track to. Mel Bartels

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If you wish the scope to continue tracking while you make handpad button corrections, you must first active the guide mode by flipping the mode switch (now hit left mode button) momentarily to the left. This is after you put the handpad in one of the guide modes via the keyboard. Otherwise the handpad will act to simply move one or the other motor in the direction you desire.                            Mel Bartels

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GuideArcsecSec only applies when the handpad is in guide mode and guide mode is turned on by the left mode switch.  MsArcsecSec applies only when the handpad is used in microstepping mode to move the telescope.  Tracking doesn't involve any of the two above values. Mel Bartels

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Q.  I would like to use some mode in which: - speed is controlled by GuideArcsecSec and drift is not applied  What is this mode?

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If you are using the handpaddle, then yes, you will fall behind the sidereal rotation of the Earth. If you are slewing via the menus, then the scope will keep up during slews.       Mel Bartels
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Software expects the circuitry to be powered down during startup sequence. Detection of unexpected signals on the handpad line is treated as defective or no handpad. The consequence without this detection is that the program often takes off with a move, and with no handpad to stop the move, can only be stopped via powering down circuit, starting up again, centering object, and doing a reset to equat. Mel Bartels 10383

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handpad CW + HsSpeed = handpad focus fast plus handpad CCW + HsSpeed = handpad focus fast minus

handpad CW + MsSpeed = handpad focus slow plus handpad CCW + MsSpeed = handpad focus slow minus  Mel Bartels

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wireless handpad ...I have the Ming Xmit and Receive pair using 4-bit encoders now functioning on the bench, using the original handpad wiring. I added a circuit to the handpad which latches the state of the 4 data lines, and compares this latched data to the current state of the handpad.  When a difference is detected, a Xmit enable pulse is sent to the Ming Xmit board, and the latch data is updated.  I also developed an analog circuit using a quad op-amp! This scheme develops different voltages for each data line into a summing amp, followed by an AC amp, then a window comparator.   -Jay LeBlanc

This rf handpad works exactly like the hard wired version, except that if you power down the handpad, or the rf signal becomes blocked from the receiver during a slew, the scope will continue to slew. (I found that ever once in a while, my body will interfere with the xmit signal.)  Depending on your scope, you might consider installing limit switches.  I have a lot of run time on the origional 9v xmit battery, and the system works wonderfully, with no stinking hand pad wire to get tangled up in the dark.

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I recently finished a hand paddle that uses a pic and matrix keypad to interface to the scope drive system. Because there is pic the paddle is able to move in "diagonal" directions by alternating the outputs to scope drive. It all works on the bench but I have yet to comlete hooking it up to my scope. I've put together a little web page that describes it at: http://sgoldman.mystarband.net/PIC    --Steve Goldman

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Added mouse control. Wireless operation at the eyepiece is now possible. A wireless mouse like the gyro-mouse can substitute for both the handpaddle and a motorized focuser controller. Note: these functions subject to change as provision is made for grand tour and scroll functions!!!     Mel Bartels

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Dan Gray's RF Handpad

HOME POSITION:

A.  (Looking at your config.dat)...your altazimuth coordinates and equatorial coordinates disagree big time.  The altazimuth coordinates are the motors' positions. The equatorial coordinates are the sky's position. So when you turn on tracking, there is a large slew in order to make up the difference.  The starting altitude is something like 138 degrees, according to the config.dat posted, with GEM flip turned on. For a fork mount with siderostat option turned off, it should never be above 90 degrees - the declination of the pole. One must do a reset of the GEM flip to turn it off, then answer yes to 'reset to equat', then save the config.dat.

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HOT KEYS:     List (at bottom of page)

HOUR ANGLE:

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If you do a 2 star init with an equatorial mount, and have even the slightest deviation from the pole, you may get large longitude and HAOffset values. Even the tiniest fraction of a degree to one side of the celestial pole will totally reverse the offsets by 180 degrees, or some very large number. This is no way affects the pointing of your scope.   Mel Bartels

+++  From the Guide users group:

Q.  Hour angle is defined as the angle, measured *westward* along the celestial equator, between the meridian and the hour circle of the
object. Using your definition, you'd run into trouble when it comes to sidereal time, which is defined as the hour angle of the FPA.  So it runs westward from 0 directly overhead to about 6 on the western horizon and appears on the eastern horizon at about 18 and runs up to the meridian at 24 (0).  Stephen Tonkin

A.  I think our definitions of LHA (local hour angle) are different. My definition read in hours, minutes, and seconds either east(-) or west (+) of the meridian. It tells you at a glance how far from the meridian, and transit the object is.

I agree that your description of LHA is technically correct. But for the last 17.5 years that I have been driving this 2.3 meter telescope we have had displayed on the control computer what we have called LHA. The PC-TCS Users Manual defines LHA as "simply LST-RA for any given telescope position, therefore, Hour Angle is positive west and negative east of the meridian."  This may not be the classic definition but it is very useful in any case.   Dennis Means

A.  Stephen is definitely right as to the "standard" definition of LHA as an always-positive quantity. But your definition appeals to me; using this, you can look at, say, "-3:14:16" and immediately know that the object will be transiting in a bit over three hours.   Bill Gray

INITIALIZE:               http://www.bbastrodesigns.com/operate_initializations.html

All mounting types need 2 inits.  At startup time, scope.exe offers to calculate the two inits for you based on mount type.  So if you say equatorial mount, scope.exe will create two inits (you can see them in config.dat after you exit the program) based on your latitude/longitude/timezone et al settings. Mel Bartels  

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When doing) a 2 Star Alignment (you)  must optimize for the following:

1. the matrix inversion and directional cosines work best with stars 90 degrees apart in both axes

2. to avoid refraction problems, stars should be at least 30 degrees elevation

3. must avoid all poles, ie, of the scope and of the sky

3. most accurate towards coordinate system equator (if altazimuth, then 2 equators to consider) for instance a good compromise for altaz mount at mid-latitudes:

star #1 to south at 25 deg elevation (breaks refraction rule just a tad)

star #2 to west at 50 deg elevation (would like higher elevation but getting to close to scope's pole)

-in all cases, a crosshair eyepiece used to high accuracy is the most critical parameter         Mel Bartels  9708

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First, the overwhelming issue is always pointing accuracy when setting the nits.

The differences between 30 deg and 50 deg above horizon are several fold.  Consider the impact on azimuth: as the degrees above horizon increases, the azimuth accuracy decreases. Eventually at the zenith, azimuth accuracy is degraded to infinity!

The Z1-2-3 is all about correcting errors between the primary and secondary axes and offsets in altitude and azimuth.

The mechanical axis is what is actually moved about when you init, but you really report the optical axis' results, when in an altazimuth, involve the tiertiary rotation (field rotation) axis. So more error here as compared to an equatorial.

But the equatorial suffers greater from azimuth offset errors because init'ing in one hemisphere tends to drive large azimuth errors in the other
hemisphere.    Mel Bartels

....use the i key to display the initializations...   Dale Eason

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I use a barlow with an eyepiece with a crosshair in it.  If you do not have such an eyepiece, they are easy to make, but in the meantime, just place the guidestar at the edge of the FOV.  All you are really needing is a reference point for keeping the star stationary.        Chuck Shaw

+++  EQ

+++ EQ Alt/AZ

Never use Polaris for a star to reset your coordinates with (GEM or Alt/Az) or to use for inits (for alt/az). Very tiny errors in having it perfectly centered can introduce very large errors in RA, which screws everything up...If you were aimed at the NCP (i.e. assumed your mount was perfectly polar aligned and the scope was aimed at the NCP (not Polaris), and you told your mount it WAS aimed at polaris, you introduced a large error in RA, and almost a degree error in Dec. By the time the software got thru with the coordinate calculations to tie RA/Dec and Alt/Az in the sky, it was really confused (as I assume you were <grin>)

Pick something further from the pole (and also stay away from the zenith).   cs 9553

+++  EQ/AltAz

Q.  On my Alt/Az scope, when I do inits, I often forget to do an Altitude Offset. This results in good tracking, but terrible goto's. Since I believe its the same bit of code for both Alt/Az and EQ mounts, does this mean if you have an EQ mount, and you do an Init 1 & 2, that you will need to do an Altitude Offset as well    James Lerch

A.  Less necessary for equatorial mounts as the simple 'reset to equat' usually guarantees accurate altitude, ie, declination... Mel Bartels

+++ EQ/AltAz

You must have 2 inits in order to track and goto. These 2 inits are needed in order to translate between scope and sky coordinates. Now, you can do these 2 inits manually, or have the program do them at startup for you by assuming certain conditions. For instance, the 'adopt equatorial mount' and 'adopt altaz mount' and 'reuse old inits' all either create the inits based on conditions in the configuration file, or reuse the old inits from the previous session.

+++ EQ / Alt/Az

Q.  When I initialize my equatorial mount I first do a polar-alignment and then point it at a known star. I then do a Reset to equatorial coordinates. Is this correct? If so, what’s with all the "Init" stuff in the program? Dobs?      Soren Madsen

A.  That's correct.  Yes, the init stuff and so forth are for dobs (alt-az)     Mel Bartels

+++    Alt/Az

 Q.  A question about initializing on two stars...when the scope is centered on a bright star, then initialized through the handpad, and then centered on a second bright star and init 2 done, is it necessary to slew between these stars? My scope does not have encoders, so there would be no way for the scope to know how much it move if I declutch the AZ axis and manually slew it.    Norm Willey

A.  yes - the scope must somehow 'know' the altitude and azimuth of the two initialization stars selected - either through encoders, or through slewing (or you can take a guess using a compass and inclinometer and hope for the best)  Mel Bartels   3020

+++   Alt/Az

+++   Alt/Az

+++  Alt/Az

+++  Alt/Az:

I suggest that first you set the scope to a known altitude and azimuth, then set these values with Coord ->InputAltAz, then Reset-AltAz.  This will give the scope a rough idea of where it is looking.  Then do the initializations on two stars, the value you then get for your position should be much closer.  Ultimately you can automate the whole process with a slew file but it may be better to get it working manually first.    Chris Rowland  11293

+++  Alt/Az

Whenever you get into a situation where tracking and goto are very bad and resets happening all over the place, then the inits and scope position are bad. Kill the inits with the 'k' key,  manually enter altitude and azimuth values (eyeballing is good enough to get going), and try the init sequence again    Mel Bartels   #10245  

have you first deleted ALL older initializations in the program? I forgot this sometimes ,too, and than the older inits would added to the newer, and the scope goes crazy.... Willi Wacker

+++  Alt/Az

"Here’s how I initialize my Bino-Scope:

#1 Select a bright star from the Bstar database (File/Datafile/Bstars.dat)
#2 Manually Slew the scope over to the star and roughly center it
#3 Using planetarium software, I find the star’s Local Atl/Az coordinates (Palm Pilot App)
#4 I enter the star’s local Alt/Az into Scope.exe (Coord/inputAltaz)
#5 I reset scope’s Alt/Az to the input data (Reset/AltAz)
#6 Set Handpad mode to Init 1 (Handpad/SelectHPMode/C (init 1 on))
#7 Back to the eyepiece, Center the star and hit upper left option button
#8 Select a Second bright star from the Bstar database (File/Datafile/Bstars.dat)
#9 Set Handpad mode to Init 2 (Handpad/SelectHPMode/D (Init 2 on))
#10 Manually Slew the scope to the second star 
#11 Center the star and hit upper Left option button
#12 Display inits to see if they seem reasonable (Init/DisplayInits or Hotkey I)
#13 Perform an Altitude Offset (Init/altOffset or Hotkey A)
#14 Select nearest Messier Object (File/Datafile2/Messier.dat)
#15 Slew to object (Move/Equat or Hotkey 1)
#16 Mentally do a little ‘Happy Dance’ when you see the object in the eyepiece      James Lerch

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Q. What does the third init give you?
A.  If you do a 2 star init, the software auto-generates the 3rd init based on the 2 stars' positions. By doing your own 3rd init, you can improve accuracy, particularly close to the 3rd init position. Any time you have more than 2 inits or positions to analyze, you can calculate the Z1Z2 errors.  Mel Bartels
+++

When initializing, the latitude and longitude enrties in config.dat only matter if you are doing an equatorial alignment. This is because scope.exe uses the lat and long to build initialization points.

When you do an init to the sky, the sidereal time is critical. That star is moving! You can fudge this if you wish by entering 0 for both sidereal times, then doing a 'reset equat coord' after centering on an object.

What the initialization does is to tie equatorial to altazimuth coordinates at a particular time. So that's why you have to enter Ra, and Dec, then enter Alt and Az, and a time for these coordinates to match. Mel Bartels

+++  EQ

A.  Not necessary. Taki's routines builds a third reference point for you based on the first two inits. If you can do a third init that is more accurate than the built one then it may be of some help, otherwise, my tests of plausible scenarios years ago showed that it caused more harm than good.   Mel Bartels

+++  EQ

..for a non-GEM equatorial...2 init points at HA +3 hrs, dec 60 deg, and HA -3hrs, dec -30deg would be ideal. Mel Bartels

+++

Q.  is there a way to "reset to equatorial coordinates" via the handpad? 

A.  No. You have to walk over to the keyboard and hit the 'r' key.      Mel Bartels   10245

+++  EQ  

1 GEM start      2.  reset to equat on a star (alkaid)    3.  goto brillinat star (mizar)    4.  center       5.   do the third init    6.   local goto is , in my case and opininon , improved to 1 arc minute over three got ( with reset to equat each time on the new object, alioth, merak duhbe )   Vincent

The local init feature was put in just for this reason - I use it a lot myself. It can make pointing within a 15-30 segment of the sky extremely accurate, down to 1 arcminute rms.  Remember you can accumulate as many inits/analysis points as you wish, and use the menu option to adopt the closest init/analysis point as one of the inits. After you accumulate a few inits/analysis points, this can make pointing very accurate.  

+++  EQ

Q.  I set up using the equatorial mount option, but then did init1 and init2 to get the polar mount error.  When entering init1 (with scope pointing at Betelgeuse) it immediately moved about 3 degrees in declination and then said that it was tracking on Betelgeuse. I don't understand this. If I've just told it that it is pointing at Betelgeuse to do the initialization why does it zoom off, especially by this amount?? This was before doing init2. Any suggestions ?

+++   EQ

+++  EQ

+++

Q   Do you know a way to kill just one init ? ( the third ? )

A   To kill an init, quit the program saying 'yes' to save config file. Edit the config file and remove init 3 line. Restart.     Mel Bartels

+++

INVERT OUTPUT:

Make sure that you have InvertOutput in config.dat set properly otherwise when you first turn on the circuit, all 8 windings between the two motors will power on, and cause a tremendous current draw.  InvertOutput should be 0 if using my board.  Mel Bartels

+++

InvertOutput inverts the output of the parallel port, so that high becomes low and visa versa. Depending on what electronics you have you may need to have the output inverted. An improperly inverted output will turn on all eight stepper motor windings, each drawing the maximum current from the power supply. This can be a fair amount of current!      Mel Bartels

+++

KEEPALIVE CIRCUIT:

Added new config.dat variable: KeepAlivePPortPin. To disable, leave at default value of zero. When 1, 14, 16, or 17, a repetitive signal is generated on this parallel port pin, to be used as a keep alive signal to external circuitry that otherwise will shut down the power to the motors.  This prevents the motors from being powered unless the software is actively running.  Mel Bartels11604

+++

I uploaded a schematic for a circuit to automatically turn on/off your scope motor power. Its located in the files area:  The schematic is in the files area, Files > circuits > keep-alive circuit>heartbeat_schematic.ppt. It takes advantage of the new heartbeat signal provided by the Oct version of scope.exe.
 
I'm sure you all know the dangers of leaving your scope electronics/motors powered with the computer turned off, or scope.exe not running. Mel's board relies on proper outputs from the parallel port to regulate current to the motors. Without computer control, the motor circuits can be badly damaged in a relatively short time.

The new cicuit should prevent this from happening by automatically disconnecting power before damage can be done. A few seconds after the heartbeat pulse stops arriving, power is turned off.  Specifically, its designed to protect from:

- leaving motor electronics on with the computer off 
- computer crashes (or the battery dies) while you're in the house thawing your hands (this happened to me last winter)
- accidental disconnect of the parallel port while motors are on (I've tripped over the cable in the dark several times)
- loss of 7805 logic power on Mel's board (my 7805 overheated one summer day and shut off

I have this circuit installed on my scope and it works great.  Larry Bell  11812

+++

LIMITS:      Hard Limits      Soft Limits

Hard Limits

Q   I went ahead and added in the microswitches myself... Work like a CHAMP. One thing to note - when you slew into them, it WILL shut off the motor (quickly), period. And that leaves you with a rocker etc jammed up against the switch, so you will need to now back it off by declutching your system.  Paul Shankland    10043

A.  The hard limit switches are for emergency cutoff of the motor. You have to supply an override switch then reverse motor direction to get out of the situation. 

The software provides soft limit switches that will also stop slews if you go past limits. You can recover from this by using microstepping on the handpad.   Mel Bartels  10059

+++

there is provision on the circuit board that I sell for limit switches that break the power to the power transistors.   Mel Bartels

+++  

I have a simple question,,,:0) Do the holes labeled  j-3-4,,5-6,,7-8 need to be jumpered on Mels PCB?     Steve Davis

They are not jumpered on a standard issue PCB from Mel. They are for half/full step and alt/az limit switches and stuff like that. I just looked at one in the shop.   Lenord

Two limit switches on the circuit board: altitude/declination and azimuth/right ascension. Closing the switch or making the jumper across the limit switch solder points on the PCB will prevent current from flowing to the motor in question. There is no limit switch for focuser/field rotator at this time. You can add one external to the PCB if you wish.   Mel Bartels  4731

A You need to put another NC (Normally Closed)  push type switch in series with the limit switch circuit and mount it inside the drive box. Whenever someone drives the mount to the limit, You just need to make sure the controller is cleared (not trying to drive the mount) and a push of this "OVERRIDE" switch will allow you to slew away from the limit condition.   Ken Hunter  10046

+++

Soft Limits

Q.  I was trying to set the software limits of scope.exe. I worked only with one axis (AzLowLimitDeg and AzHighLimitDeg). I used to init the scope pointing only one bright star and reseting coords.

When the scope was init, I moved it through the handpad to one RA limit, then read Az coords on screen (192.00). I opened config.dat and wrote AzLowLimitDeg 192.0000.

I run scope.exe again and checked the behaviour was Ok. ..., with the handcontroller moved the scope to the
other side of RA axis..... I wrote 20 in AzHighLimitDeg in config.dat file.

When I run scope.exe again and checked the behaviour was strange, the handcontroller was disable in the correct direction.

I have never used alt-az coords with my GEM so I do not have much knowledge about them, but I understand Alt-Az coords as absolute coords, I mean Alt-Az limits always will be the same (192 and 20).  Obviously, I am doing something wrong (probably) or scope.exe manages limits wrong (rare).     Antonio.  12035

A.  Make the low limit 20 and the high limit 192. Scope.exe will not understand if you have the high limit less than the low limit.  Mel Bartels

+++

Changed behavior when attempting to move beyond altitude and azimuth limits when in grand tour or scroll modes. Before, a message would appear requiring a keystroke to clear, now, two warning beeps are played, while a message is displayed briefly, then program execution continues. If doing a grand tour or scroll tour at the eyepiece, if you attempt a move beyond the limits, you can now move to the next object in the usual manner after the warning beeps.  Mel Bartels.

+++

Added ramping distance to altitude and azimuth software limits.  So, the scope will start to ramp down as a limit is approached, so that the scope finishes the ramp down as the limit is reached.  Mel Bartels

+++

Q.  I was wondering if the AZ limits would allow for several turns CW or CCW.  That is -720 and +720 for two revolutions either way. My circuit board just blew three TIP120 so I can't test this out myself right now. 

A.  The software limits in azimuth must be between zero and 360. There is provision on the circuit board for hardware limits which would be
normally open switches.  Mel Bartels

LONGITUDE,  LATITUDE:

Q  What sign (+ or- ) does scope expect for West longtiudes? 

A   You should enter longitude as 78 (not -78)

+++

Q.  Like you I'm East of the Greenwich meridian and from a reply I had from Mel I understand that the program was really designed for West longitudes (ie USA). Mel suggested entering  my longitude as 186 degrees rather than 174 east and it seems to work.
+++

Q.  I am located : Lat. N 52deg 18' 40" = N 52.311     Long E 4deg 50' 12" = E 4.833

I looked in the source code and if the longitude is negative it is converted to 360 - Longitude when it is read from config.dat.  The result is that a -ve value, such as -6 deg will be converted to a +ve value, i.e. 354 deg and will be saved as this. So negative values can be entered - in config.dat at least. If you enter the site from the menu then no check is done so you need to get it right.   Chris 

+++

Southern Latitudes are negative   Andy Martyn

+++

LX200:

LX 200 commands are sent via a serial connection between a computer running a planetarium program (Guide, Cartes du Ceil, Earth Centered Universe, Megastar, Starry Night, etc, etc) and the computer running Scope.exe.  The instructions to slew are in Hr Min Sec format.  This works fine for the declination numbers since the units are degrees and the resolution is 1 arcsecond.  The units for Right Ascension however are time and the resolution is 1 second, or 15 arcseconds * cos(declination).

To obtain better resolution, Guide.exe and Scope.exe were modified to send and receive an additional 2 decimal places, ie Hr Min Sec.xx.  This gets the resolution on the RA axis down below 1 arcsecond.

Run Guide and then hit Alt-J and type in FORCED_LX200=3  This will cause Guide to send the 2 extra decimal places over LX200.

The above is for the windows version of Guide.  If you are running DOS Guide, it already at the higher resolution. Ben Davies

+++

LX 200 Command set:   LX200 commands supported by Scope

+++

Scope.exe can act or mimic a lx200 so that it receives commands from other external planetarium and control programs. Set up the lx200 communications port values in config.dat, plug in a serial null cable, and open a channel in your planetarium program to control a lx200 scope.  Mel Bartels

+++

Added ability to read hundreds of a second in the LX200 command Set Right Ascension. This gives better than arcsecond precision to Right Ascension.

+++

+++

A.  Signal ground, transmit and receive should be all the lines needed. For a simple null modem just wire transmit to receive and receive to transmit.   Marty Nemi

+++

+++

 if using the shortform of lx200 (LX200_LongFormat 0) commands input from external control program, might be as coarse as 1 arcminute.  Mel Bartels

...there is a long coordinate format available in the lx200 protocol (LX200_LongFormat 1)- the planetarium program needs to be aware of it and toggle it on.  Mel Bartels

+++

LX200BaudRate. Some controlling programs now offer a choice of baud rates for LX200 control, allowing for faster transfer of information with less consequent impact on microstepping. Mel Bartels

+++  

LX200SlewHs: if no slew stop received from planetarium program, this limits slew distance - in halfsteps  Mel Bartels

+++

A couple more things you might try if you want to get StarryNight working.    (during long slews, StarryNight will report the scope has disconneted or that the slew failed)

1) A faster computer running scope might allow the system to handle the faster LX200 updates/polling. When I run scope on my 225Mz Pentium Scope.exe is able to handle the fastest polling rate in SkyMap Pro (I think its 1 update every tenth of a second). When I tried an older 60Mz pentium, this setting did not work. Either the computer speed or the quality of the serial interface made a difference.

2) ensure you're using the latest drivers for your computer's serial port. Apparently many original serial port drivers are terribly inefficient. Someone on this page sent me a great set of "improved" public domain serial port drivers. They are MUCH faster and more capable. I've misplaced the web address, but still have the zipped file w/drivers and instructions.   Larry Bell

+++

A.  The first three numbers are right ascension (RA). The second three numbers are declination (Dec.). The next piece of text is the abbreviated object name, Cr307 and Ru120. The last numbers are the visual magnitudes of the objects.

_Changed the behavior of the guide mode GuideStaySaveOn to be aware of LX200 guiding commands. Now, if LX200 guiding is already underway by a master controlling program, when GuideStaySaveOn is turned 'On', the current guided too position by the LX200 guiding commands will be adopted as the base position, setting drift to zero, starting the guiding arrays from scratch, and guiding will proceed as before. When GuideStaySaveOn is turned 'Off' the guiding efforts are preserved in memory ready for analysis.  Previously, the only way to access the guiding efforts was to restart the program using the command line option to load in a guiding efforts file.  Mel Bartels

_Added ability to read right ascension seconds to three decimal places in the LX200 protocol, ie, :Sr 05:16:59.345#

+++

MECHANICAL:

For azimuth drive shafts that should be tapered, aim the taper at the junction of the azimuth axis and the bottom of the plate that the drive shaft supports. For many designs, that will be an angle close to 10 degrees.    Mel Bartels

+++

About the last word in cold weather lube is Dupont's Krytox. It is good to liquid nitrogen temps, contains teflon, will not get hard, or run and never wears out. The little sample they are willing to send you ( free ) will last a lifetime of telescope servicing. A few molecules of this stuff on aluminum threads and they will never gall again. http://www.miller-stephenson.com/home_008.htm Andrew Aurigema 

+++

Try polycarbonate if you want to make clear covers. You can float it on hot vegetable oil at about 250 deg F to get it soft then just drape it over the form. Heat guns work great too just not too close. Too close and you get bubbles in the plastic.   Andrew Aurigema