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MICROSTEPPING:         http://www.bbastrodesigns.com/operate_microstep_config.html 

The # 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

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If you set a single microstep on my system to 0.2 arcsecond, then max speed is 80,000 * 0.2 arcsecond or 16,000 arcsecond/sec, or 4.4 deg/sec.    Mel Bartels

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The 40 microsteps is not for every situation. It will slow down the max microstepping speed, so don't go to 40 unless you need it because your gearing is coarse (under 1000:1). I continue to use my 20 inch at 20 microsteps as the best balance between max Ms speed, smoothness, and accuracy.    Mel Bartels  367

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HsRampStyle 1          HsTimerFlag 1            MaxDelay 1700

MinDelay 600            HsDelayX 1                HsRampX 1

InterruptHs 5             HoldReps 5                 HsOverVoltageControl 0

MaxConsecutiveSlews 5

MsPowerDownSec 180          PWMRepsTick 22                                       AvgPWMRepsTickOnFlag 1

MsDelayX 6                             MsPause 66                                                  Ms 4

MaxIncrMsPerPWM 8           MsHsToggleIncrMsPerPWM 16             MaxPWM 100       

PWM[0] 100 : 10

PWM[1] 100 : 60     

PWM[2] 100 : 100

PWM[3] 60 : 100                    Don D'Egidio

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When I was tuning the 17 size Vexta motors for the G11, I had an ammeter in series with the common lead from the motor so that I could monitor the current going only to the motor. I would get the motor running the fastest by setting the 2 Motor Track speed close to what Scope.exe told me was the max value. Then, while holding the motor in my hand while I was adjusting the MSDelayX, I would find the value that felt the smoothest. Next I would adjust the MSPause value until there were no perceptible vibrations and make a note of those values and the current reading. There would always be several combinations of MSDelayX and MSPause that would give very smooth motor running, so I would use the one with the lowest current reading, as a start, until everything was on the mount and a trial could be done with all components on the telescope. At that point some more adjusting would be done until the mount ran smoothly, gave slews with no motor stalling, and used the minimum current needed to achieve that condition. I do like Mel's software because of it's ability to be configured to almost any motor and mount available. Still, those Hurst motors were very stubborn in adjusting for smooth running.  Don D'Egidio

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try to get the PWMRepsTick value up as high as possible.  If that means setting MsDelayX to 1 and MSPause to very small numbers, then do it. The motors tend to run much smoother.   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 (PWMRepsTick) 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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If microstepping, then speed controlled by the MsArcsecSec value. If halfstepping then speed controlled by MaxDelay MinDelay values. Mel Bartels

MsArcsecSec

1. Set the microstep rate to the maximum possible (use the M hotkey and set
the maximum value suggested).

2. Try moving the scope in the Microstep mode using the handpad. If the
motors stall then the maximum microstep rate is too high. In this case:

3. Reduce the MsIncr parameter using the Motors | MsParams menu.

4 Goto step 1 and repeat until both motors will move at the maximum
microstep rate without stalling..   Chris Roland 11417

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In the end we have to find the balance between current draw, reasonable margin for adjusting smoothness and saturation of the CPU, which means:  -High enough PWM values that do not strain the CPU and give us margin to adjust Microsteps, but might result in fairly high current draw -MsPause values that lower current draw and leave us with a PWMRepsTick of approx. 30   Berthold  

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Q.  Is there any restrictions in less than 10 MS/step? Does it need to be and even number of MS?

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Q.   ...if the displayed PMW count is right when tracking or when tracking is turned off.  

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PWM's of 15/14 is a little low.  The 36/36 is a lot better although I've gone as low as 10 with decent results. Mel Bartels

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Q.  I'm trying this on a 386-16 The pmw count can get up to 50 but the average is around 16.should I turn off the avr. PWM's and set it manually to 25 or so.?

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Setting MsPause and MsDelay to the lowest possible values will give you maximum PWMRepsTick which for my 486DX/50 is about 180 

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AvgPWMRepsTickOnFlag: if 1, then auto-averaging of the PWMRepsTick will occur, based on the actual number of PWM repetitions per timer tick as averaged over 3.5 seconds; if 0, then the PWMRepsTick value as entered in the config.dat file will be used.  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 so, with a 286, you should be able to get 9-10 PWms per tick out of the software.

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The microstepping parameters control the voltage to the motor.

Voltage is PWM value * MsDelayX / (MaxPWM * MsDelayX + MsPause)

Typically you adjust MsPause to control microstepping voltage, and adjust MsDelayX to control the speed of the PWMs.  Mel Bartels

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MaxPWM value is the maximum that any PWM[] value can be.  However, PWM[] values can be less.  This gives flexibility in assigning PWM[] values to help precisely position rotor for each microstep.  Most people including me use 100 for MaxPWM and PWM[0] as it is convenient and gives enough resolution.  However, 200 can be used. Higher than that will cause fastest microstep speed possible to be rather low, also, if MaxPWM is too great, convention DOS that scope.exe is run under will start to run out of memory to hold all the PWM[] values. 

When maximum is set to 100 you can vary the microstep only by 1 up or down, so the smallest amount of change gives you 1%. When you put a maximum on 200 , you change by 1 thus 0.5 % difference possible between 2 microsteps                         Mel Bartels

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Heavy torque on the stepper motor shaft retards the shaft position by percentage of load vs capacity, so if torque loading is 30% (not unreasonable) then when rotor is between windings, the rotor will lag behind by 30%. By increasing the current draw when the rotor is between windings, an attempt is made to fight this. At least that is the idea behind the PWM values in the config.dat files that I use.    Mel Bartels

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Try MaxPWM of 50 and 200, but 100 seems to work best for my laptop; a 486DX50.  200 showed promise because it appeared to be much quieter, however the steps did not become smoother.  Now I know its because of the additional overhead on my machine

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On a 33mhz machine, it is sometimes needed to lower the max PWM to 80. It just depends on what the PWM's are when you are tracking. If you go to 40 ms, have MsDelay at 0 and MsPause to 1 and the PWM value that show on the screen when tracking is too low, your steppers will act funny and be untunable. Too low being like 15 or so. Lowering the max PWM for all of the step values and the MaxPWM setting will raise the PWM displayed when tracking up to a higher value.  An old 386 would not run well on 20 ms so Mel tuned them by using 50 as a MaxPWM and a value for all of the steps.             Lenord Stage

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The PWM controls the amount of voltage in each microstep.  The percentage of ons vs offs control the current going to the motors. For instance, a PWM value of 50 with a MaxPWM value of 100 will do 50% current, as will PWM of 150 and a MaxPWM of 300. The MsPause is a value tacked onto the end of the PWMs. So a MsPause of 100 with PWM of 50 and MaxPWM of 100 is the same as PWM of 50 with MaxPWM of 200. MsDelayX is a multiplier - if 2 then all values are doubled. This makes faster computers work the same as slower  computers if you simply increase MsDelayX until the PWMs per timer tick are the same.               Mel Bartels

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it takes a certain amount of PWM numbers to get the motor to sense the current. That's why that final PWM[] number always seems high.  Mel Bartels

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The PWM[] value of 100 was selected to give enough resolution to the other PWM[] values. That is, if you pick the extreme case of PWM[0] = 1, then there are not a lot of choices for the other PMW[] values! But 100 is not a magic number. Certainly 50 is a fine choice for slower machines, and even down to 25 will work.

Remember that inside the program, the actual PWM[] number is the configured PWM[] value times the MsDelayX, so the following are equivalent:

PWM[0] 100
MsDelayX 1

PWM[0] 50
MsDelayX 2

But the first example gives you twice the resolution for the other PWM[] values, which, you may or may not need.

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The MsDelayX was added a long time ago when PCs began running too fast, and the PWM[] values  consequently had to be several hundred. If you try this (make the PWM[0] value 500 or a 1000), you will run out of memory to build the PWM[] arrays. The PWM[] array output bit patterns are allocated to a memory location for fastest retrieval when doing the actual microsteps. I could recreate the PWM output bit patterns on the fly, and avoid the array completely, but then the minimum computer would become a Pentium 166 or so.    Mel Bartels

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MsDelayX cannot be fractional. It is a multiplier for PWM[] values.  Every PWM[] pulse that goes out, is delayed or multiplied in the code by MsDelayX.  So PWM[0] of 100 with MsDelayX of 1 is same as  PWM[0] of 50 with MsDelayX of 2.    Mel Bartels

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Setting MsPause and MsDelay to the lowest possible values will give you maximum PWMRepsTick which for my 486DX/50 is about 180.     Andy Martyn   8162
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MSDelayX is a direct multiplier of PWMs.  It is the number of times the PWM[x] value is read before it is executed.  If you increase the PWM Value, you will also need to adjust down the MSdelayX value accordingly for the same performance to get the same PWMRepsTick value (i.e. how many PWM pulses get crammed into a cycle, etc.).  Changes to MsDelayX also require adjusting MsPause to control the current and smoothness   Chuck Shaw

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Simplified, MSDelayx is used to keep the arrays of PWMs reasonably small on faster machines. Setting Msdelay at ie. 2 and having a PWM of 50 equals to having Msdelay 1 and PWM of 100. Since on a slow machine you are not likely to get prohibitively high PWM arrays, there is no need to set Msdelayx to anything but 1.

The PWMs control the voltage sent to your motors . Also simplified, each microstep is divided into 1 PWM and 1 MsPause. Each PWM is divided into a certain number of parts (Ons and offs) and so is MsPause, defining such the voltage the associated Ms will receive.

Lets say for example (simplified again!):
Ms1 has associated PWM1 with a value of 100
Ms2 has associated PWM2 with a value of 50
MsPause stays constant all the time.
Ms2 (or better the associated motor winding) will receive 50% of the voltage that MS1 received.

The point is that the higher the PWM values are, the more you strain your CPU as well. The lower they are the less margin you have for adjusting them for smoothness.  Interestingly using the same motors, a high PWM value on a slow machine will result in higher current draw then on a fast computer. I guess it must have something to do with the way the waveform is generated.

In the end we have to find the balance between current draw, reasonable margin for adjusting smoothness and saturation of the CPU, which means:  -High enough PWM values that do not strain the CPU and give us margin to adjust Microsteps, but might result in fairly high current draw -MsPause values that lower current draw and leave us with a PWMRepsTick of approx. 30   Berthold  

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MSPauseX – dummy loop at end of each PWM[] loop to take up time.  After equalizing the microsteps, use an ammeter to adjust MsPauseX till the current reading is no higher than the rated wattage of the steppers when the system is in track mode   Chuck Shaw

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Lowering the numerical values (of MSPause and MSDelay) gives you more juice to the steppers. Raising the number values takes away juice.   Lenord  Stage

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MsDelayX sets the overall frequency of the PWM (the Humm) 

With stepper motors (any coil/inductor) as the frequency applied rises so do the resistance of the coil, thus you need to adjust the duty cycle to compensate to get the current flow back up, as current flow often = Torque.          James Lerch

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With a pointer on the motor shaft, and the invertoutput set correctly, select MSDelay=1, use the tracktest (now Motors | MSSpeed) and set the rate to step the motor at about 20-30 ms/second. Then vary MSPause up and down in value looking for smooth motion at the lowest current reading (this is a tradeoff, too low  current will get jerky). 

Then increase MSDelay=2, and repeat looking for the best tradeoff between smoothness and low current.

Keep increasing MSDelay and repeating the MSPause/Current experiment till you feel things are not improving. I suspect with a 30mhz machine you would not go beyond MSDelay=2 or 3, and for your 50mhz machine maybe you would get as high as 3-4 in your testing.....

Also watch the PWMReps value being displayed. If its not in the 30-60 range, decrease ALL the PWM[x] values in your array by the same  percentage (i.e. reduce them to 50% of their current value, or maybe 70% or 80%, etc..... That will help increase the PWM's being displayed. A very low PWM will work, but its hard to get smooth motion at very low PWM's being displayed. Setting the PWMRepsTick in config.dat does NOT change the PWM's being displayed.... The PWMRepsTick in config.dat is part of what tells scope.exe how fast it can track in ms mode. The displayed PWM value is showing you what your CPU is able to do. When you are all done tuning, set the PWMRepsTick in config.dat to the value shown on the display...

Once the MSPause/MSDelay setting are picked, then move to tuning your ms's to get smoothness there, using a very slow ms/second rate (0.5 to 1.0 ms/second).   Chuck Shaw 2777

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From my understanding PWMRepsTick is derived from MsDelayX. Basically decreasing MsDelayX will increase PWMRepsTick with the maximum value you can achieve on your machine reached when MsDelayX = 1 (About 180 on my 486 laptop). As you change MsDelayX and thus PWMRepsTick you change the frequency of the pulses sent to the motors which changes the frequency the motor tends to vibrate at which you can hear via a change in the noise pitch of the motor. It would seem that a MsDelayX = 11 is produces the frequency at which vibration is at a minimum for your setup.

MsPause will change the effective current you supply the motor with so that by increasing MsPause you will decrease the current used by your system which may make the motor run smoother but will definitely reduce torque.  Increasing MsPause may also reduce PWMRepsTick to a lesser extent than changing MsDelay but I cannot remember at the moment.

After all the above I truly believe the best way to set MsDelayX and MsPause is to use the AutoMsParms feature which will automatically work out the values for you if you give it the PWMRepsTick and % current values you want to use.  Andy Martyn

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MsPause adds dummy loops to the PWM cycles. Those dummy loops strain the CPU, which is why normally you should keep them low on slow PCs.  An indication for, whether your computer keeps up is the PWMRepsTick.  If it goes below 25 then smoothness of microstepping will be seriously compromised. I got a decent balance between smoothness and power consumption at around PWMRepsTick 35 on my old 386.

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MsPowerDownSec 600 in config.dat that will keep the motors powered if no movement for 10 minutes  Mel Bartels

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How did you set your MsDelayX and MsPause???? It has been my experience that unless these are set pretty close first, it is impossible to get any good results with setting the PWM[x] values......

The technique I have found to get pretty close values for MsDelayX and MsPause is as follows (this came originally from Tom K.):

1. Hook up an ammeter to the power to the motor. attach a cardboard pointer about 8-10" long to the motor shaft (you need a good visual indicator for the first part of this technique, NOT something super accurate for movement measurement....)

2. Start with the default values for PWM[x] in config.dat. Use the test routine to run the motor at about 20-30 ms/sec

3. Pick a value of MsDelayX, and then use the menu test routine to vary the value of MsPause up and down until the motion is smooth. Watch the current going to the motor, and try to get as low of a current reading as you can, while still achieving smooth motion. Write down the MsDelayX and MsPause value that goes with it.

4. Pick another value of MsDelayX, and repeat step #3.

5. Repeat step#4 as many times as you feel you want to.....

6. Update Config.dat with your best combination of MsDelayX and MsPause, and  THEN (and ONLY then) you can attach a laser pointer or an encoder to the motor to adjust the individual PWM[x] values to achieve individual ms of equal size.

7. Set the rate to zero ms/sec, and then use the +/- keys to move the motor one ms at a time to adjust the PWM[x] values. You can take as much time as you like between commanding the motor to the next ms.

8. Once you think you have things about right, repeat step #3 to verify the MsPause value you are using with the MsDelayX still gives smooth motion at 20- 30 ms/sec. If yes, you are done. If you had to tweak anything while repeating step#3, you will also have to repeat steps 6 and 7.....

This is an iterative process, and one that should NOT be rushed. Enjoy it, the results will amaze you and really be worth while at the eyepiece!!!!   Chuck Shaw   5630

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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

A.  Yes   100 % means only relative and not the absolute value of the current. The beauty of mels system is that it uses Pulse width modulation to achieve microsteps. What is meant by 100 % is that the pulse is "on" at all times and motors draw as much as they can. and by 50 % means that the pulse train has "on" states 50 % of the time or in other words the average value of the current is 50 % of max . If u use a 6 V stepper on 12 volts the current drawn by it in the 100 % will be double the current it will draw at 6 V .  Higher voltage is prescribed so that u can manage a higher RPM. .  Sanat Kumar-

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Q.  Are the following parallel port "out" commands exactly the same for micro-step one?

 Out 1
 PWMRepsTick = 40
 MaxPWM = 100
 PWM[1] = 90
 MsDelayX = 2
 MsPause = 50

 Out 2
 PWMRepsTick = 40
 MaxPWM = 200
 PWM[1] = 180
 MsDelayX = 1
 MsPause = 50

A.  MsDelayX doubles each PWM output, so the two options are essentially identical. el Bartels

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Q.  Can you give a brief description/explanation of how 'auto adjust ms parms' works? 

A.  Well, there are three values

The pwm value which is the frequency of the pulse width modulations (times this number by 18 to get pwm freq per second, ie, a value of 40 means close to 600 Hertz) 

The mspause which is the dead quiet time at the end of every pwm (adjusts voltage or current level into the motor) 

The msdelayx which allows for equivalent smaller pwm values which is good for the software so that you don't push the old DOS memory limits, ie, a pwm[0] of 50 0 with msdelayx of 2 is same as pwm[0] of 100 0 with msdelayx of 1 the auto adjust ms parms menu option calculates these values for you, given a few seconds of time, based on your desired current percentage and desired pwm number   Mel Bartels

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Auto Ms parms, under the control section.  Here, you input the desired PWM repetitions per timer tick, and the percentage of current draw you wish going to the motors, and the program will do its best to settle in on the appropriate MsDelayX and MsPause values. Values are updated every 3 seconds, so allow a few seconds for the program to reach the best numbers. Desirable PWM reps per tick range from the lowest suggested of 10, to the best range of 30 to 100, with 200 as highest suggested. Percent of current draw should be minimized so that only the current required to microstep track is actually pulled from the power source. For instance, with 6 volt motors and a 12 volt supply, current % should be no more than 50, and can often be 20%. In combination with the new auto PWM reps tick averaging, this should speed up  configuring the microstepping parms.             Mel Bartels

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Maximum microstepping speed is MaxIncrMsPerPWM.  At some point before reaching this speed, the program will switch from PWMs to halfstepping, this speed being MsHsToggleIncrMsPerPWM.  MsHsToggleIncrMsPerPWM should be less than or at most, equal to MaxIncrMsPerPWM.     Mel Bartels

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make MaxIncrMsPerPWM equal to half of your total microstep number, and make MsHsToggleIncrMsPerPWM about half of that. Mel Bartels 2795

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Microstepping switches from pulse width modulation to halfstepping at MsHsToggleIncrMsPerPWM. Microstepping speed using halfsteps can increase to a maximum of MaxIncrMsPerPWM. Either employing pulse width modulation or halfstepping, the current to the windings is timed by the PWMs that occur approximately the same count per bios clock tick. This is to be distinguished from halfstep slewing which is timed differently.   Mel Bartels

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Lets assume: PWMRepsTick = 50

MaxIncrMsPerPWM = 8

MsHsToggleIncrMsPerPWM = 4

Ms = 32, and microstep size = 0.2 arcsec

When the scope is tracking the scope will switch to halfstepping using timing based on the PWM rate when it hits  MsHsToggleIncrMsPerPWM. This will occur when the number of microsteps required to be moved per PWM exceeds 4 which equates to a tracking speed of 18.2 * 50 * 4 * 0.2 = 728 arcsec/sec. 

The drive will then continue in tracking mode using halfsteps timed by the PWM rate until it gets to the next limit set by MaxIncrMsPerPWM at which time it will exit tracking mode and go into slew mode. The tracking speed at which this will occur in the example given will be 18.2 * 50 * 8 * 0.2 = 1456 arcsec/sec.   Andy Martyn

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MaxIncrMsPerPWM sets the acceleration rate for microstepping slew. This parameter is used by Scope when it moves the mount on "its own", that is as the result of the difference between target coordinates and where scope is pointing at. If you press your handpad button in microstepping mode there is no acceleration - it simpley picks the rate given by MsArcsecSec and applies it flat.  Now, look at the above parameter (MaxIncrMsPerPWM) : it tells program how many microsteps can it add EVERY PWM (not bios tick!). There could be lots of PWMs in case of fast PCs. Even with my ancient 486 I'm reaching 250+. Now 5 microsteps doesn's sound much, but accumulated over every PWM that is a LOT of microsteps in a very short time!  200 PWMRepsTick means that every second there is 200*18.2=3640 PWMs.

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100 microsteps or 256 or 1000 microsteps can be implemented with my code, but then the issue becomes one of managing all those steps and trying to tune them. I think 32 microsteps the optimum compromise.Mel Bartels

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Q.  have been trying to tune some RS Component steppers cat#440-442, 200 step 5v 1 amp. I am unable to get them to rotate smoothly in microstep mode. I have tried 2 laptops, a Toshiba 486 33mhz, and an IBM 2.0 gig p4. Using a 12volt battery power supply.In all cases I get a sort of cogging rotation, slow/fast, a bit like a second hand that does not smooth out despite many hours trying various combinations of parameters. I have tried 10, 20, 32 and 40 microstep versions, and every conceivable figure for mspause and ms delay, had currents up to 1.5 amps flowing and I have had pwm figures from 15 through to 100. Has anybody ever tuned these to work smoothly?

A.  Most likely causes of erratic motor operation:

--- mistuned software configuration     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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There are 18 ticks per second, so you want the motor to feel several hundred to a couple of thousand PWMs per second for smooth motion.  The software may be a tad slower now but should not be too much slower - this is because of the additional code in the microstepping function that automatically turns off the non moving motor after 5 seconds, and that automatically switches to halfsteps for tracking when necessary.Mel Bartels

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Try to pick motor speeds where you have a whole number of microsteps per timer tick which occurs 18.2 times per second)                Mel Bartels  

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AccumMs. are the motors' absolute position in accumulated microsteps  Mel Bartels

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Q.  Why 32 microsteps max? Is there a specific reason for this number?

A. Yes, there is a reason. I use integers for fastest speed for the slower computers. It is possible to run over the max integer at 32k if you have larger MaxPWM and higher count of microsteps per fullstep.  I will probably convert these numbers to 'long' values when the slowest computer in use running scope.exe can handle them with decent speed.  Mel Bartels

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The ms parameters (PWM[x]) can be tailored to each motor.  However the parameters that control current (MsDelayX and MsPause) are common to both motors.   Chuck Shaw

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Q.   ...when I turn tracking on (just having the RA/AZ motor connected it just sits there juddering erratically. 

A. Have you adjusted the microstep speed, via the menu option msspeed? Go to a little lower speed.   Mel Bartels

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you can calculate % of current by:
MaxPWM * MsDelayX  /  MaxPWM * MsDelayX + MsPauseMel Bartels

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Go to Motors | msparms    use the + and - keys to advance/decrement single microsteps

Check the display in the lower right to verify that steps are being made

After you cycle through all microsteps (beginning at 'A00', for example)  you will be on next fullstep indicated by a 'B00' and so forth

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

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Q.  Is it possible to turn off microstepping? 

A.  You might try setting MsHsToggleIncrMsPerPWM 1. No guarantees!  You might also try a microstep setting of 2 with PWM[0] and PWM[1]                    Mel Bartels

I have done that for setting up a drive testing system and it works just fine. PWM[0] was 100:0 and WM[1] was 100:100     Chuck Shaw

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Changed how the end of each bios clock tick cycle terminates the pulse width modulation. This cycle occurs 18.2 times per second. Now the PWMs are immediately terminated and the motors set to power off condition. Mel Bartels

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Microstepping power down occurs regardless of motor's shaft or rotor positioning. Before, power down would only occur if rotor positioned on a fullstep. If the motor is not commanded to move in microsteps during an interval lasting MsPowerDownSec, motor will be powered down. Any subsequent microstep command will power up the motor.Mel Bartels

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..that backwards microstepping jitter and possibly missed steps came from the MSPowerDownSec. Apparently when moving fairly slowly, as the motor would reach a winding and then immediately power down, the motor would sometimes kick back to the previous fullstep thanks to residual magnetism in the stepper motor windings and torque on the motor shaft. So I have changed this to not power down the motor for 5 seconds. This seems to be the ticket. So for equatorial mounts, the declination motor will humm in place for 5 seconds, then power down, after concluding a slew. Mel Bartels 109

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In addition you can turn off microstepping completely for the declination motor via the menu system. This is handy if you have a perfectly  aligned scope with no practical declination drift.   Mel Bartels

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MICROSTEPS - ADJUSTING:    http://www.bbastrodesigns.com/operate_microstep_config.html 

The "Ms" area shows the number of microsteps per timer tick (occurs 18.2 times per second) for altitude and azimuth motors, the winding from 'a' to 'd', the microstep within the winding for altitude and azimuth motors, and the quarter step correction for altitude and azimuth motors in decimal fullsteps.     Mel Bartels   4201

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The microstep display line on the lower right hand side of the screen will always indicate what winding and what microstep you are on, for each motor.  For example, this screen shows the altitude/declination motor on winding C microstep 0, and the azimuth/right ascension motor on winding A microstep 0.     Mel Bartels

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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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To step through individual microsteps, go to the menu option:
motors | msparms and use the + and - keys to advance or retreat individual microsteps.
Use the 't' or 'q' key to quit.                mb

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If using an equatorial mount, tune your motor with the other motor powered down, since most of your time will be spent with the declination motor powered off.  mb

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what you tune (on the bench) with a touch of drag on the motor shaft is fine for use at the scope. The steps mainly have to be smooth and roughly similar in size unless the gear ratio is very small in the 300:1 area. I've never gone to great lengths to tune my motors at the telescope (a 20 inch f/5) as local seeing effects obscure issues below 1 arcsecond anyhow.  Mel Bartels

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I totally agree with Mel's opinion that smoothness is more important than totally even ms's. I use my Alt/Az scope almost totally for CCD imaging with my CB245. I have not gone to any greater lengths than using a pointer on a motor to get the smoothness and even-ness settings. Visually (watching the 8" long cardboard pointer tip thru a magnifying glass) gets me very close to even ms's (I use 20 ms's). My step size is only 1.5 arcsec/full step though, so I rationalize the very slight potential unevenness as being buried in lots of other errors like seeing, etc.. I suspect I will remeasure things with a mirror on the motor shaft and my laser collimator bouncing off the mirror just to see how accurately I CAN get the steps, but that is stuff for cloudy nights.....

I use a simple and quick technique passed on by Tom Krajci for getting the motor motion nice and smooth:

Hook a pointer up to your motor (cardboard, about 8" long or so) Configure an ammeter in series with the power going to the motor (use the highest range initially).  Use the Test Motor routines [note: these routines are no longer in the software- use MsSpeed from the menu - bd] to start spinning the motor at about 20 to 30 ms/sec.  Pick a value for MsDelayX, and then vary MsPause up and down watching both the motion of the pointer tip and the current the motor is drawing.

Write down the MsDelayX and MsPause value combination that gives the smoothest motion for the lowest current drawn. As current decreases, the motion will be less smooth. At too much current, the motion is smoother. The idea is to lower the current till the motion starts to NOT be smooth, the raise it a little. You will be surprised at how changing MsPause by only ONE number will make a big difference when you get close to the optimal values....

Repeat this for other values of MsDelayX. Then pick the best of the different MsDelayX/MsPause combinations.

THEN lower the rate the motor is spinning from 20 to 30 ms/sec to around 1 (or less) ms/sec and play with the PWM [x] values to get the ms's each of equal size.

Finish up by re-checking the MsDelayX and MsPause settings at 20 to 30 ms/sec again to see if MsPause needs to be tweaked a tiny bit.   Chuck Shaw

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Some of the things that I have learned with my motors are.  First that the step sizes get much more equal if you use higher current.  I run my steppers at 12 volts and they are rated at 5.2V 7.28Watts which means I'm pulling .6 amps at 12 volts instead of the .1 that’s recommended.  This gives me good motion both forward and reverse.  Second my steppers would not draw constant current through the halfstep.  The 1/4 point drew less and the 3/4 point drew more for all four full steps so that the current would oscillate from .4 to 1 amp as the motor microstepped.  The slower the step rate the more pronounced the Oscillation.  The motors turned very smooth and even on the bench but this change in current was evident when the motor was mounted to the scope.  I fixed this by altering the PWM values.  I got the microstepping equal then I took the ones that were drawing to much current and lowered both sides of the PWM values so as to maintain the same ratio.  So now not all of my MS have a PWMmax of 100 some are lower and the current draw is smooth and so is the motion on my scope.  I did use the QSC to help equalize the 1/4 steps. This helped but I still want to measure some more.  You have to make sure that the laser is mounted really firm and the motor vibration does not change the motor orientation.

One last thing.  If you can measure the current draw during the 4 fullsteps you might find that the large change in half step sizes is due to a big change in current for phase A B C & D.  You can control this with the (current compensating) software also which should change the half step sizes.  It is explained briefly on Mels web page under configuring the software close to the end.  It was page 8 of 10 on my hardcopy.                          Andy Martyn

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Made laser spot analysis over a four-fullstep interval. (That was tedious!...and for two motors!!) Set the first laser spot (microstep 0 of the first fullstep...where winding A is energized) as zero and measured the distance of every laser spot from this 'zero point.' I did this all the way up to the next time the A winding was energized, at microstep zero. This point was the end of my four fullstep analysis. The distance between the first and second point (first time A winding was energized, and the second time the A winding was energized) was my baseline distance...and I divided that distance by the 80 microsteps in between to determine the "ideal" spacing of micro, quarter, half, and full step positions.

Then I loaded all the distance data of the 80 microsteps in a spreadsheet and compared the real world distance data to the 'ideal' positions. Based on the difference/deviation of real world data from 'ideal'...that was the basis for my QSC values for each motor. (Actually I did a linear fit to the data deviation, every quarter step.)

I've uploaded the spreadsheet I used to do this analysis to the list's "microstep" file area...it's called: QSC.XLS.    Tom Krajci  2682

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Start scope.exe. Using MsSpeed in the menu set microsteps at 1/10 (.1) microsteps per second. This will give you 10 seconds between each microstep and allow your test apparatus to stabilize between readings. If necessary, stop down your laser pointer with a piece of tape with a pinhole in the middle.

At step 0, make a pencil mark in the center of the dot. As the program advances, keep marking each microstep in a like manner, making marginal notes where necessary.    Bob Norgard   http://home.gci.net/~rnorgard/Scope/Microsteps.html" 

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Q. Did you "curve" the paper you took the data points (microstep lengths) on to match the radius of the data points or did you just keep it flat, and use a long projection distance to keep the tangent error small? (I assume the latter)


My projection distance was about nine feet, with the mirror on the shaft (to double the angle sensitivity of the setup). I did not bend the  paper...and for analyzing movement over only one motor step (1.8 degrees for a 200 step motor) you can get away with that.

Even for four fullstep analysis I did not bend the paper...but I did apply a trig correction to the data to reduce the distance values on flat paper into angles at the motor shaft. In that case I needed to keep track of where along the trail of spots on paper that the projection angle between the paper and laser spots was perpendicular...that was my 'zero trig correction factor' point, and I adjusted from there...which is not hard to do with a spreadsheet...the relationship/correction factor is something like (in Excel spreadsheet language):   =1/((TAN(C2*PI()/180))*(180/PI())/C2) ...where in this case C2 is the cell value in my spreadsheet that represents the angle distance of the laser spot from the 'zero trig correction point' (the point where the laser line of sight is perpendicular to the paper).            Tom Krajci    2710

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I take ideal position in mm, and i read the ideal angular value , i put the value of current on the cos curve, and finally the PWM to take. I wanted to tell this first to you, since i did not know the right words in english, but i feel it is a good method, and it is not iterative : for example the spot never stops or go"back" , as it did when i tried other method ...One advantage is with this kind of PWM table, an example of what i get is this :

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you can use the quarter step correction (QSC) to fix microstep positioning, particularly if the microsteps are fairly evenly spaced but yet tend to bunch up such that the middle microstep comes early or late.

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.14 amps current consumption while microstep tracking is close to ideal for many people - it's more a measure of the friction requirements of the drive reducer than anything else     Mel Bartels

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I see significant improvements going from 10 to 20 microsteps, and others like Tom Krajci have seen benefit going to 40. This is not only in terms of smoothness but also in terms of absolute positioning. As you mention, the software allows compensation to make each microstep meaningful     Mel Bartels

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Q.  The motor has not load. Is it necessary to do the adjustment with the motor under load?? 

A.  Highly recommended, even if you have to put a little clamp on the stepper motor shaft while tuning the microsteps. Mel Bartels

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I found that the way to adjust the microsteps is go into the MsParms menu where you can advance the stepper motors one microstep at a time using the + and - keys and adjust the PWM values in the same menu. This feature only works for the Altitude motor output so to tune the Azimuth motor you have to plug the Azimuth motor into the Altitude output. The standard config file only has one set of PWM values but you can create another set of values called PWMZ that will be for Azimuth motor while the existing PWM values will drive the Altitude motor.

I always start the tuning with 10 ms. I get that evened up and double it, (Press D on the MS#). After 20ms is even, I go to 40.   ls

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You should mark the A0, B0, C0, and D0 positions first, based on actual pointing, and not on calculated position. These are fullstep positions and are motor/gearing dependent, not software or voltage dependent. Now you can go back and adjust the microsteps to evenly fill the gaps between the fullstep positions. Variations in fullstep position from the ideal need to be compensated with the quarter step correction (QSC).  Mel Bartels

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general advice:  Have read through the answers to this question and I can say from my own experiences tuning the motors can be a frustrating process and what you have experienced is not uncommon. From my experience:

1. Try and get motors with halfstep sizes that are within 10% of each other. QSC can make the motion smoother but it you will still have unequal step sizes between difference half steps.

2. Use the minimum number of microsteps you can get away with. The more you have the harder it is to get steps near the halfstep position accurate.

3. If you find you are running out of tuning resolution you can increase the PWM values from the standard 100 to 200 to give more fidelity in your tuning steps. Also increasing current helps resolution so when setting up in AutoMsParms set a high PWMRepsTick and high % current value.

4. Always set the middle microstep to have equal current applied to both coils ie 100:100 and then adjust your values so that you get equal microsteps for the half step each side.

5. Always make sure you are making the adjustments for microstepping over the same coils ie from a0 to b0. If you really want to get technical, get the best PWM values over each of the 4 full steps ie a0 to b0, b0 to c0, c0 to d0, and d0 to a0 and then average them.

6. When marking and measuring the microstop positions always go in one direction which means if you want to measure a position a few steps backwards in the opposite direction, take more backwards steps than you need, and then step forward to the required step. Andy Martyn

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One way I like to do it is to set up a laser pointer system (or use a magnifying lens and precision scale with a long pointer on the stepper shaft). Make a mark, move the stepper motor two halfsteps, and make another mark. Now divide that up into 20 steps. Go into microstep track parameter mode, and set it up to do 1 microstep per 10 seconds.  Tune that microstep so that the pointer goes 1/20th of the way. You have 10 seconds... :)                     Mel Bartels

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Generally, when expanding the number of microsteps, only lower the last value a bit. So if PWM[9] = 30 and you wish to go from 10 microsteps to 20, make the new PWM[19] = 27 or so. The proportion the other values accordingly. If you get into real trouble, a linear progression will work, but the motion will be a tad uneven. But you can adjust from there if nothing else seems to work. Generally the PWM[] numbers will follow a sin/cosine type curve or progression.    Mel Bartels   378

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Stepper motor construction 'issues' affect the PWM[] values. You will see, with certain motors, the middle PWM[] value shift earlier or later in the microstep PWM[] series. My basic rule is to make the PWM[] values whatever it takes to get the steps as smooth as possible. Sometimes really funny looking numbers result. A different motor will act differently, but as long as you can reasonably tune the microsteps for smooth motion at the eyepiece, then you ought to consider things successfully configured.     Mel Bartels

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1. Set your half step size.

Andy Martyn   http://www.spin.net.au/~afmartyn/software.html     Andy Martyn

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1. Input guesstimate PWM[X] values for each microstep and then use the AutoMsParms menu to get the motor to turn as quietly and smoothly as possible. I found that the higher PWMRepsTick and higher current values gave me the best result. I ended up with a PWMRepsTick of about 180 and 100% current. The main reason I use 100% current is that I am running 24V motors with only a 17V supply.
   
   2. The next step is to adjust the PWM[X] values to get the microstep sizes right. To indicate the step sizes I Fattached the laser to the output shaft of the motor and projected it onto a piece of paper about 5m away. I tuned both motors separately and averaged over the 4 coils to get the best possible result but you may get good result by using the same values for both motors and tuning over just one coil.
   
   3. To tune the azimuth motor you must plug it into the altitude output of the control box as tuning via the MsParms menu only works for the altitude motor.
   
   4. Using the + and - keys in the MsParms menu move the motor to position a0   and mark the position of the laser pointer on the paper, move to the halfstep position a16 and place another mark, and then move to the fullstep position b0 and place another mark. Then divide the halfsteps into 16 equal microsteps and mark them on the paper. While the marked microstep distances may be different for the two halfsteps by using this method you can keep the middle PWM or halfstep value at 100:100 and then fix the different sizes using QSC.
   
   5. Now step through the microsteps from a0 to b0 and adjust the PWM values so that the laser points at the correct microstep mark on the paper. After you have done this record the PWM values. This can be a fiddly process and you will probably find that results will change depending on the direction you are moving and the adjustments you make. My hints are to increase MsPowerDownSec to 100 sec so that the motor does not power down at full step positions, always move the motor in the same direction, and after you have made a correction check it by backing off a couple of microsteps and then advance it again to check the adjusted microstep position.
   
   6. Repeat the previous two steps for the other 3 coils, ie b0 to c0, c0 to d0, and d0 to a0.
   
   7. Average the recorded PWM values for each microstep and input these values.
   
   8. Next you work out QSC which is worthwhile if you see large differences between halfstep sizes. First point the laser at the paper on the wall for fullstep position a0 and make a mark. Advance the motor through 4 fullsteps until you get back to a0. Divide the distance between the two marks equally into 16 equal distances which gives you the ideal quarter step sizes. A point to note is that because the motor is moving a few degrees over the four steps and the laser is projecting onto a flat surface you will small tangential errors. You can adjust the marks to allow for this error, or make an adjustment when you are working out your QSC values.
   
   9. Now just step through the microsteps and mark on the paper where the laser says the quarter steps are.
   
   10. Calculating the QSC values is then just a matter of measuring the difference between the measured quarter mark and the ideal quarter mark and then dividing it by the fullstep distance. For example if the distance covered by the 4 fullsteps is 600mm then the full step size is 150mm and the differences for the first 4 quarter steps are 0 (the first value is always 0), +10, +5, and -10, then the QSC values are 0, 0.067, 0.033, and -0.067.
   
   11. This completes the process for the azimuth motor and you transfer the PWM values for the microsteps into the PWMZ values which drive the azimuth motor.
   
   12. You now plug the altitude motor into the altitude output and repeat the whole process again for the altitude motor.       Andy Martyn

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If you find at lower current you have repeatability problems with microstep positions (when microstepping from one direction or the other...the laser spot doesn't fall in the same place for a given microstep), and that increasing current improves the situation, then you are at least partially solving the problem.  If there is no improvement in repeatability in microstep position with higher current, then something else is the culprit.     Tom Krajci

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I am using a 133mhz pentium. First to setup your microsteps, Mel has changed this to menu access. Instead of setting the teststring n the config.dat, you go to MOTORS. Under MOTORS arrow down to MsParms. Here you will begin your microstep adjustment. Andrew was correct for my fast pentium, I needed at least a MaxPWM of 200. You may require an even larger value. My final microstep values are as follows:  PWM 57, MXdelay 5, MSPause 90, MS 20, 5 and 5 for the HSdelayX and or HSrampX up and 200 for the MAX PWM. 

PWM (0) 200,0

PWM (1) 200,88

PWM (2) 200,122

PWM (3) 200,143

PWM (4) 200,152

PWM (5) 200,160

PWM (6) 200,168

PWM (7) 200,177

PWM (8) 200,185

PWM (9) 200,193

PWM (10) 200,200

PWM (11) 192,200

PWM (12) 183,200

PWM (13) 176,200

PWM (14) 168,200

PWM (15) 160,200

PWM (16) 151,200

PWM (17) 144,200

PWM (18) 120,200

PWM (19) 84,200

Q.  My problem is that when set to microstep test mode the first 4 steps are backward to the zero step. The next 16 are forward.

A.  Try some other rotor angles on the stepper motor and if possible try another stepper. Poor or misaligned stepper internals can cause this.

Next, look at the circuit board and make sure that there is no leakage of current from one side of the winding to the other. For instance, if winding A is turned off, make sure no current is flowing through the A- winding.

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A.  Just adjust the MsPause to maintain the same PWM repetitions per timer tick  as the old machine. Use the auto adjust ms parms to make this automatic.   Mel Bartels

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MODEM TO MODEM SERIAL CONNECTION:  

I encourage anyone that wants to use two serial ports on their old laptop and has an unused internal modem to give this a try, it works GREAT!!!!! The only catch is, of course, that the 2nd laptop (running the planetarium or autoguider program) must also have a modem to interface with... 

I put together a small webpage to describe the technique, what I have to do to configure my system to use this capability, and provide a place to download Dave's program he donated. You can access it at http://www.ghg.net/cshaw/modem.htm

Ben captured the information on his circuit on his website, and the techniques he uses to configure his laptop (which is slightly different than what I need to do). His website is at: http://ben.davies.net/computers.htm The two website are also linked to each other.      Chuck Shaw

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Q.  I cannot configure modem. (in DOS)

A.  Do you have a WinModem? Some of them will not work at all in dos.   bd
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Q.  are there some PCMCIA modem cards that work in DOS, or do I have any  other options?

A.  I am successfully using a quatech pcmcia serial port adapter under DOS. It has not been a cakewalk to install it.  I ended up booting DOS from a floppy with all the drivers and enablers.  It works, and 2 serial ports are very handy with scope. -Luca Grella

A.  http://www.quatech.com/catalog/rs232_pcmcia.php                ftp://ftp.quatech.com/manuals/ssp-100.pdf http://www.quatech.com/support/discontinued.php   Don D'Egidio

A.  I use, is a docking port which has two serial ports built into it.  Works great without any modems problems.  Gary Mueller

^{MOTORS – STEPPERS}:      http://www.bbastrodesigns.com/steppermotors.html         Connecting the stepper leads     more     Specific Stepper Motor recommendations      Correct Stepper Wiring       5 Phase Steppers

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Q.  If you have a 6 or 8 lead surplus motor how can you tell if it is 2- or 4-phase?

A  Mel's program is set up for four phase steppers.  Bob Rubendunst

A.  Almost all 5, 6, and 8 wire steppers are unipolar or 4 phase motors. They only vary in the number of discreet power leads - 1, 2, or 4 going to the windings.  Mel Bartels

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You can easily measure your static and dynamic friction with an adaptor and a small (let's say 40 oz-in or metric equivalent) torque wrench.  You can get a suitable one (cheap, not super accurate, almost throw-away) for very little. Try a couple times reading the maximum reading just before the gauge drops and the scope starts to move for your static and take the average. Take the lower reading once it is moving for the dynamic.  That gives you your start and stop requirements. As Mel stated, the rest is moment of inertia which is only a factor in acceleration and can be compensated for with gearing and slowing down/speeding up your ramp-up speed.  Howard Douthat

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In general, higher winding resistance steppers use less current, tend to be smoother and less noisy, but have a harder time going very fast. So pick your best compromise! You can add resistance in series with the stepper winding if you wish to decrease current usage by the stepper (current usage by the power resister can be substantial) and make the motor spin faster (time constant of the stepper goes down).     Mel Bartels

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Q  This motor got exceedingly hot after about 10 minutes so I shut off the system (the motor is cooling down as I write).  What can I do to remedy this heating problem?  

A.  Too much voltage/current is being supplied for the motor's tastes. You can either

1. reduce the power supply voltage
2. use the current limiting add-on circuit by Jean-Charles Vachon
3. use series power resistors - one power resistor of high wattage per motor winding
4. manipulate the configuration settings in config.dat so that the software controls the current going to the motors; do this by a. setting the HsDelayX to a smaller value so that the motors start up slewing faster
b. increasing the MsPause value so that the current is reduced while microstepping  Mel Bartels  494

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NEMA frame size 17 specs ..... are a little smaller than a NEMA 23 frame size stepper.  You can buy steppers that size from a number of sources. www.candhsales.com had them IIRC. Like $9.00 each, 200 step, torquey, reasonably quiet and work with Mel's PCB.  Lenord Stage

5-7 volts         single stack (magnets)      1 amp or less      unipolar        3/4" long shaft         .250" shaft dia       400 steps (.9 degree)     dual shafts           Lenord Stage

You can tell which leads are part of each coil by shorting 2 leads at a time while turning the motor shaft by hand.  If the motor offers more resistance to turning, then the leads are common to a coil.  If you get only 1/2 the full resistance, you have a center tap and one end.  Jay LeBlanc

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Question: If at one end of a long shaft I attach  stepper motor of normal torque with 6 leads ....and at the other end attach another identical motor. Can the leads be reversed so one will run CCW and the other CW from the same input signal from the program?  I would want to double my torque without doubling the size of the steppers. (space consideration)

A.  Certainly! I did that with an equatorial platform (two motors being pulsed off of one set of pulses). Worked great! You need two sets of TIP120s though, one for each motor......Each "pair" of TIP120's are tied together at their bases and both conduct at the same time. Otherwise running the windings in parallel from a single TIP120's output can screw things up....(at least it did for me).  Chuck Shaw
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Bipolar / Unipolar Steppers  

Specific Motors

5 PHASE STEPPERS

Mel's board won't drive 5 phase motors, but his software will.  Ben Davies

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Q.  Can Mels board be modified to drive these motors directly or is a intermediate driver required?

A.  If you 've got some basic electronics experience, it will be an easy job to modify it yourself.  The original circuit uses for the RA motor parallel port pins 6, 7, 8, 9 and for for the DEC motor parallel port pins 2, 3, 4, and 5. As you can imagine, to drive 5 phase steppers, you need to use extra  pins. These are for RA pin 17, and for DEC pin 16.

Now let's get inspirred by Mel's original design here, http://www.bbastrodesigns.com/cot/steppercircuit.html, and an other  important source of inspiration here: http://www.cs.uiowa.edu/~jones/step/circuits.html.

Follow the first hyperlink above, and check out the second circuit diagram. (I strongly recommend people also to build the  optocouplers, this can limit damage in case of trouble with power supplies). In your modified design you copy for every parallel port pin the left part of this diagram. These are from left to right the 1/4 part of the 74LS04, the optocoupler, the 220 ohm resistor, the 4k7 resistor and the other 1/4 part of the 74LS04. Skip the rest of the circuit. (And of course, you will put these 74LS04's in separate casings). 

Now we 'redesign' the second part, the power section to drive the coils. For every coil on your 5 phase stepper, we need half of the H-bridge design. Go to the picture 3.14 in the second hyperlink.  This circuit diagram was designed for bipolar  steppermotors. Copy everything from 'x' on the left side until the coil. Fix 'x' to the  right (exit) of the right hand 74LS04 of the first circuit part.  Build this for pin 2, 3, 4, 5, 6, 7, 8, 9, 16, and 17, and you can make your 5 phase steppers run. The only other thing that needs to change is one 'config.dat' setting: "MotorWindings 5".

The motor wiring: I hope your motors have got 5 wires. I believe 5-phase steppers can come with 5, 6 or 10 wires, mine have 5. When you have got the wire order OK, you can force your motors to step one-by-one by manually triggering the parallel port on the controller. The steps should be small and in equal size and direction. 

Actually, in my own circuit, I needed to put in some small modifications. I am using transistors I scavenged from an old line 
printer. Make sure you are using Darlington transistors (that's what they actually are). If the BD769 is hard to find, try the  TIP120.  Components really aren't too critical, play with them. You will get your motors running.   Marc Fokker

MOTOR STALLING:

Q. The declination motor ramps up, but at a point stops rotating, as the software ramps down the motor starts again. I guess this is stalling?    
A.  Yes, this is stalling - the MinDelay is too low (or fast) of a value. You can adjust this through the menu option hs parms. Mel Bartels

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MinDelay  Unless you are using more than 12 volts or flywheels, getting the MinDelay down to 350 is about normal, if not better than average, from what I have seen. The faster the steppers spin, the less torque they have.                               Lenord Stage

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MOUNT:

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When an object approaches the zenith, the azimuth is basically fixed, and the altitude creeps up to 90. When it crosses zenith, the azimuth must change 180 degrees very quickly, so the altitude can start creeping down from 90 to 0. If the object is too close to zenith, the scope can't slew the azimuth around fast enough. Mike Lindner   129 . ...The zenith problem with alt-az mounts is due to the axis of the mount being different from that of the earth. With an equatorial mount, the problem doesn't exist, even at the pole (assuming the mount is reasonably well polar aligned). 

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An Alt-Az mount having perfect orthogonally between the optical axis and the altitude axis and perfect orthogonally between the altitude axis and the azimuth axis can indeed access any part of the sky. But if there is any misalignment between the optical, altitude and azimuth axes then there is a region near the zenith that the optical axis cannot point to.    -Dave Rowe-

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To comment on the three mount options:       I strongly recommend roller drives. Either the split ring or the horseshoe or yoke will work fine. Pick the one that you think you will be most inspired to do well. I personally like the horseshoe because it is easy to build very accurately, though it is bulky. Leaving completely assembled and rolling in and out of a small trailer (always packed with the essentials so that you are ready to go at moment's notice) might be a possibility. In the end though, your execution of the design will matter more than the particular design you selected. --  Mel Bartels

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Q.  Does anyone know an equation to calculate the cg of a "C" shaped figure (my alt bearings) in terms of inside diameter and outside diameter of the "C". I can't even remember how to describe the shape mathematically! The bearings will be 180deg of a circle.

A.  To find out a center of gravity of any shape without knowing its mathematical description or having to make lot of fancy calculations or reading communist literature, there is simpler method possibly sufficiently accurate for practical cases.

Cut out desired shape from cardboard, not necessarily in full size, and hang it on thread fixed subsequently to several points on the circumference. When in equilibrium draw a line extending thread direction ( vertical) across the shape.
CoG will be always somewhere on this line ( per definition).  All such lines will intersect in the CoG. All identical shapes will have CoG on the same relative position disregarding actual scale.  Vladimir Galogaza  atmfree.  
PS   This can be done with the complete telescope in order to find its actual CoG. 

A.  When I can't figure out an integral like that and need an approximate answer I usually use a spreadsheet program to "integrate" the area by  creating 100 or more slices along the curve. Use one column to create the points on top of the curve, a second to create the points on the bottom of the curve, a third to compute the area of the slices, a fourth for weighted areas. Sum the weighted area and divide by the sum of the areas and you have the balance point.  Jeff Andrson-Lee  atmfree

A.  The correct formula is the moment divided by the area. I assume that the ends of the "C" are radii. So the area of the C is the area of a ring times the fraction of a circle that the C includes (typically 3/4 circle).  The moment can be calculated by 2*[ri^3 - ro^3]*sin(t)/3. where t is the enclosed angle (typically 270 degrees), ri is the inside radius, and ro is the outside radius.

Sanity check: the center of mass should be between -r0 and 0.    Richard Schwartz  atmfree

+++ALTAZ

Q.  I screwed a stainless steel plate of 0.5 mm (0.02") thickness, for the six (three pairs of two) azimuth rollerbearings (rolerskate type) to ride on. The stainless is not hard enough to prevent the bearings from tracking 6 'grooves' into the plate. The total weight of the telescope o the bearings is about 66 kilo's (145 lbs).  Would it be better to use thicker stainless? Or is stainless simply too soft  and is there a better material to use (maybe galvanized steel)?

MOUSE:       http://www.bbastrodesigns.com/mouse.html 

Mouse won't work:     I found that config.dat had listed the LX-200 interface as being on COM1, the same port that the mouse was on. I changed the LX-200 port to COM2, and now the mouse works fine.   Allen Gilchrist

+++

NETWORK CONNECTIONS:      see modem to modem

Q.  Has anyone run this type of setup on a network rather than using Null Modem cable?

A. PcAnywhere works, as does xpc (remote control from unix workstation), but LapLink appears to bite too heavily into the cpu time and causes scope.exe to run rough. Tried vnc through windows and that was rough too, but have not had the chance to try vnc-dos yet.        Mel Bartels

+++

+++

+++

I use a 486DX2 66MHz running Scope with MS LAN Manager for DOS and PCAnywhere 5 for DOS with NetBeui protocol.  Most of the program are loading in the high memory.  This PC is controlled by a Pentium 100 with 32Mel Bartelsand PCAnywhere 9 and Scope is working fine.  They are connected with ISA LAN cards and UTP cable.     Garry Lang

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Joe,  I finally got things wired up and have two PCs serially communicating with a third. The hookup is like this: Signal ground common to all three.  Transmit from the master goes to receive on each slave and transmits from the slaves are connected to the receive of the master through 1N914 diodes.  When the master transmits, both slaves receive. Either slave can transmit to the master without seeing the others data. Looks like it is working exactly exactly as I was hoping it would. Guess I better exercise this setup a bit more to check things out. I am always worried when things are too easy.  Marty  Niemi

+++

A. With high speed internet access you can get a very reasonable remote control session going. I control a Scope I system used for imaging this way. The images are setup to automatically transfer from the remote system to my home PC as they come in. I now use a free VPN (Virtual Private Network) package called Hamachi that requires very little setup. The nice thing is that it provides a consistant virtual IP address for your machine. What I had been doing previously was having the main PC send an email to me so that when I remotely powered it up I could determine from home what IP address it had been assigned by my ISP. The VPN package also removed the requirement to fool with forwarding ports through my NAT routers. There are a bunch of remote control packages like PC Anywhere available ranging from free to $$$. I am very happy being able to work this way. My goal was to be able to start a remote imaging session and then go to bed. I have it worked out where I can con trol the dome, my CCD camera, live video that lets me check on the setup, and power on and off all of the equipment remotely. Only way for us poor working stiffs to get any imaging done and still get some sleep. I love it. Marty Niemi 

NOISE:                 http://www.bbastrodesigns.com/steppermotornoise.html

The motor attached to the scope should be no noisier than it is when held unattached in  your hand.  Mel Bartels

+++  

The best thing I have found to isolate the steppers are flexible shaft couplers from herbach.com and plate mounts from small parts.com. Alexander Urban has some decent pictures of them mounted on his web pages (linked at Mels site)  Lenord Stage 8639

+++

Tracking will be a lot louder than slewing speed. If you isolate and tune the stepper well enough though, the difference is maybe~ 50% between the two speeds. There are a lot of variables that can make that percentage higher or lower however.     Lenord Stage

+++

See if you can isolate motor more - rubber is not best - try sorbathane or keyboard armrest or similar and isolate motor shaft too.  www.sorbothane.com  available from http://www.mcmaster.com   Mel Bartels

+++

keep the flexible shaft to almost zero length - just a millimeter is all that is needed. That way there is no windup between motor and input gearing.           Mel Bartels

+++

You can add a flywheel to the stepper motor shaft to slow down the motor shaft resonant frequency, or you can add a hard rubber coupler between the motor shaft and the scope input shaft. This will absorb the motor shaft resonances             Mel Bartels

+++

I don't think they (flywheels) made a difference in noise levels. At best it was a very slight difference. Tom Krajci  40

+++ 

5. If you are able to do so, use flexible shaft couplings with the rubber insert. Those can be had from http://www.herbach.com and other places  too.  If you are using gearheads, put a piece of mouse mat between the stepper and the gearhead. Use nylon bolts.                 Leonard Stage

+++

I've applied poster putty around my alt and az stepper motor bodies, and found that it's cut the motor noise by more than half. 

Poster putty is an adhesive putty that is used to hang lightweight objects on the wall without damaging wall paper, etc.  It's sticky enough to stay in place, but the best advantage is that it's moldable to just about any shape, so I can get it into tight corners.  

Since it's always sticky, before I take the scope outdoors I'll cover the exposed putty with some plastic sheet so it won't collect dirt and grass.  Tom Krajci

+++

I remembered Berthold asking about noise coming from the gearheads. I mentioned using mouse mats between the steppers and the gearheads, thick ones, to help with the noise/vibration transmission. I also remembered Paul Shankland telling us about the gel inside of a wrist rest. That material was suppose to keep the vibrations of a stepper to a minimum, it does indeed do just that !  I now have put the gel/goo that is inside a wrist rest into the INSIDE of a gearhead. 

It required adding in a piece of galvanized sheet metal to separate the inside of the gearhead into two parts, diagonally. (I just cut it a little long and bent it ). I then used the open, separated space, to insert a piece of the gel stuff. It does work rather well           Lenord Stage

+++

- great idea to put the stuff on the inside of the stepper - I'd just wrapped the motor with it on the outside.  Not as pretty, but plenty there to deaden sound. And boy it works well! I can't hear 'em at all! As for freezing, at least the gel doesn't freeze in the 20-30 degree range outside, and it didn't harden in my fridge... but being on the outside of the motor is likely "safer" for me were it to freeze on me..  Paul Shankland

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In my setup the major source of noise are the gearboxes (250:1). The steppers contribute very little noise. I have been experimenting a lot with cork (5mm) lately and found the results quite satisfying. I "coated the outside of the gearboxes with cork and found that noise was reduced significantly. I am thinking now about gluing cork also to the inside walls of the gears.               Berthold

+++

in my hard combat against the noise, I have tested a lot of microstep values. With high values in these parameters noise becomes more and more bass and even disappears, but then the laser pointer oscillates drawing a line (not a point) in the wall. If I decrease MSPause and DelayX, oscillation disappears but noise appears again.  Other curious effect occurs when I reduce the voltage supply until the nominal motor voltage, the noise reduces but the oscillation appears again and I have to decrease MSPause and DelayX to eliminate it, appearing the noise... 

My conclusion was that MSPause and DelayX high means low frecuency PWM and two coils in the motor are being excited but with such a low frecuency that the shaft has time to move from one coil to the other, instead of keeping in a balanced position between both coils.      Antonio   7182

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I have had some NEMA 17 frame size steppers that were quieter too.  Remember, on the bench, the noise can be magnified. When on the mount and isolated well, the noise levels can be diminished significantly.    Lenord  Stage

OPERATING SYSTEM:    www.freedos.org        www.bootdisk.com    DR-DOS  $30 (the same as Novelle DOS)     OPENDOS                                            http://www.bbastrodesigns.com/operate_halfstep_config.html   win98bootfloppy

Early versions of Windows are partially multi tasking, once a program has access to the CPU it keeps it until it releases it, Scope will work with this because it will simply hang onto things while it needs it and the rest of the system stops. Later versions of Windows won't do this.  W2K will not run Scope at all because Scope needs to take control of the whole PC system, including the parallel port, Rs232 port and even the clock interrupt. In W2K, NT and XP these resources are protected and special drivers are needed to communicate with them. Chris Rowland

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HsTimerFlag: set to 1 if you wish to use IRQ 8 (dos) to time the halfstep slews, this allows for realtime (DOS) updating of scope coordinates, keyboard interruption of slews, and altitude limit checking during a slew.  Otherwise if set to 0 (for WINDOWS), halfsteps are timed by a delay loop with interrupts disabled to avoid interruption; using IRQ8.  Works perfectly in DOS, not at all in Win 3.x, and slowly in Win95        Mel Bartels

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There are some things you can do in Win9x to give more cpu power to the DOS session, including adequate memory, a fresh install of Win9x to eliminate as many of those background processes (do a ctrl-alt-del to see these processes - you only need 2 or 3 critical ones running), simple display settings, various screen savers and background schedules turned off, settings for DOS priority and processing turned up to the max, and so forth. Also, there may be some PC architecture reasons why DOS session under Win9x won't run well on certain machines. I can say that I haven't come across a machine that I couldn't get to do an adequate DOS session, but then at work, we are limited to certain name brands like IBM, HP, Compaq, AST, and so forth.    Mel Bartels

+++

Scope.exe is a dos program, and will run under win3x fine, and will run under win9x ok too, but not under win2k.   Mel Bartels 

+++

In Win3.1, you can use the interrupt method of halfstepping.  Otherwise, you can at boot up time, go directly into the command line, and run scope.exe under Dos 7, or alternatively, simply boot with a disk with DOS 6x on it (any Dos from 3 up is fine) and go from there. Mel Bartels

+++  

Running Scope under Windows:  Go to scope.exe and left click to bring up the Properties. Click the Program Tab and then the Advanced button. Check the box "Prevent MS-DOS-based programs from detecting Windows" and click OK. See if that helps.   Don Egidio

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old DOS commands like mem/c/p/p or mem /d/p that will report what's loaded into conventional memory.    Mel Bartels

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I found though was without Himem, I could not load DOS into upper memory (DOS=High), and that was eating up conventional memory. I added HiMem back into the config.sys file and the PWM's stayed up (EMM386 was the culprit for slowing down the PWMReps), and now I can shell out to DOS and run Planets, or edit, etc.       Chuck  Shaw  895

(Do not use) emm386 because it actively manages memory, and intercepts every call to memory - which my program uses quite heavily. Mel Bartels 896

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There is no usage of expanded or extended memory in my program.  (no emm)    Mel Bartels76

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These files get me 625k "largest executable program size" on Win98 DOS (DOS 7.1) Pentium 133

Config.sys
device = c:\windows\himem.sys\ /TESTMEM:OFF /Q
device = c:\windows\emm386.exe noems 
dos = high,umb,auto
FILESHIGH=15
BUFFERSHIGH=15,0

Autoexec.bat
@echo off
prompt $p$g
PATH=c:\windows;c:\windows\command;c:\scope;c:\dosguide
Loadhigh c:\mouse\mouse.exe
cd =c:\scope
scope.exe

Note:  To boot these from the floppy, copy
+++

Download these zip files and extract them to C:\UMBPCI

Then Config.sys

Switches=/f /e
dos=high,UMB,auto
DEVICE=C:\UMBPCI\UMBPCI.SYS
DEVICE=C:\UMBPCI\HIRAM.EXE
LASTDRIVE=d
FCBS=1,0
SHELL=C:\Windows\COMMAND.COM /E:1024 /P
STACKSHIGH=0,0
FILESHIGH=15
BUFFERSHIGH=15,0

Autoexec.bat
@echo off
prompt $p$g
PATH=c:\;c:\windows;c:\windows\command;c:\scope;c:\dosguide;c:\guide8;c:\mouse;
LOADHIGH C:\MOUSE\MOUSE.EXE
SET COMSPEC=C:\WINDOWS\COMMAND.COM
cd c:\scope

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If you are worried about legality, use FreeDOS (search engines will pull up the website - can't remember it at the moment).  I've tried it on a number of machines and it works great. Scope.exe should work on DOS 3 and higher.          Mel Bartels          www.freedos.org

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Try www.bootdisk.com   I used them before and got good stuff there.    Mark Hogue  9642

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A. Use Winimage http://www.assysm.com/winimage/winima61.exe  to extract it to a floppy. Chuck Hartkoph

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Q.  If the hard disk is formatted with FAT32 won't it cause problems if used with anything less than the version of DOS that comes with WIN95?                   Martyn Cole

A.  Yes, if the HD is formatted FAT32, then booting into DOS 6 will be a problem. In this case, just running off a bootable floppy is fine, or partitioning the HD, or adding a 2nd HD with the old styled formatting, are also fine.  Mel Bartels

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I've had very good luck with Windows 95/98 DOS version 7. I use a very simple config.sys with himem.sys as the only device driver. The mouse is usually not loaded but a cdrom driver in config.sys and mscdex in autoexec.bat are loaded.  Mel Bartels

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method of handling Windows 95-98 / DOS.

There is a text file in the C:/ directory (or Windows directory) named MSDOS.SYS. Back it up. Change the Hidden and Read Only attributes.  Under [Options] Change the line "BootGUI=1" to "BootGUI=0"  Add the line "Logo=0" 

This causes the computer to boot clean to a DOS screen. No Windows. Type "win" on the DOS command line if you want to run Windows.  The Windows splash screen doesn't appear.        Ben Davies  7205

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Running Scope.exe + anything else under Windows :

A) User clicks Start/Programs and windows has to load the icons for all the programs on the start menu from the disk drive.

+++

The goal was to run Scope.exe and windows programs at the same time on one PC. One example would be to run a planetarium program, scope, and maybe a video capture at the same time. Currently scope consumes all the resources of the system and will not run in a windows multitasking mode very well. Part of the goal was to use standard windows so that no other software would need to be purchased. It should also run on the typical hardware used by Scope.exe users.  Here are the results of my investigation into using a windows driver to step the motors so that scope.exe could run along with other windows applications at the same time. The goal was to write a driver that would step the phases of the motor as scope.exe does now but not consume all the CPU resources so that other windows programs could run at the same time. That required that the driver would be called at the start of every step time and the relinquish control until the next step time. In other words deterministic scheduling is needed. The time period needs to be in the few microsecond range with an accuracy of about 1 microsecond. The bottom line is I could not do it.

OVERVOLTAGE:                      also see current limiting resistor

HsOverVoltageControl: for optional halfstep high speed slewing over-voltage control; if desired, enter a non-zero value. Control line is parallel port pin #17. Value entered here will be the Delay value at which the over-voltage control line will be toggled logical high. Pick a value between MaxDelay (slowest speed or greatest delay) and MinDelay (fastest speed or least delay between halfsteps)        Mel Bartels6003

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... for microstepping the current control is already in place ala the control software. Thus except for edge rates ( the rate of current change is directly proportional to the applied voltage - the constant of proportionality is the inverse of the inductance ) there is no benefit.  For slewing there is a very large benefit to go with higher voltages. The one caveat is that it also increases the mechanical resonances of the system (the stimulus is  harder!). To overcome the latter you need to have properly flywheeled (damped) shafts. If this is done you will see a very significant increase in max slew rate.  When at the high slew rate (and when getting there for the most part) the inductance in most motors limits the actual current the phase can obtain.   Gary Myers    8005

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For the benefit of those contemplating building a circuit, check out the files area, circuits/overvoltage/ folders for schematics for a circuit that is known to work.   a file has been uploaded to the Files area of the scope-drive group.  File : /circuits/Overvoltage Switch Circuit/overvoltage_schematic.jpg  

I recommend anyone planning to add any overvoltage circuit take a few simple precautions: 1) Build with care, and test the system with small capacity batteries (9v or similar) before connecting the circuit to your system.  Simulate pin 17 by connecting between +5V and Grd. 2) 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. 3) Once you know its working correctly, connect your power supplies (hi & low) and make sure the circuit still works as expected. No load/motors connected, or use a resistive load that is comparable to your motors. Be careful not to exceed current ratings for long periods.  4)If it still works, hook everything up and try it out in the full-up system. Use an O-scope to look for glitches, transients, oscillations on the power leads as you switch from hi-low-hi. Check out all voltages including the computer power supply. If you see oscillation greater than 5-10% of the supply voltage, or oscillations that lasts more than a fraction of a second you need to find the source of the problem before using the system -- especially if you see the problem on the computer supply or grounds. Usually, you'll need to replace your power supply and/or rework your power returns to eliminate ground loops, resistive or floating grounds etc.     Larry Bell    8389

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when the program wishes the overvoltage activated, you will see pport pin 17 go to logical low.     Mel Bartels  8170

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I have not found that 6v motors being driven at 12v require the current limiting circuit. Adding it would not hurt, but a lot of us operate in this configuration and have done so for a long time without problems. The 2x voltage ops do not provide the slewing speeds that a 4x voltage config  provides, but that is the only downside I have found to taking the more conservative approach.  Chuck Shaw  2964

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My layout of the overvoltage circuit was pretty simple. I used a Radio Shack Perf board (about 2 inches square) and hard wired everything -- basically it is configured as a daughter board mounted piggy-back on Mel's board. I used a 6-pin connector for connections between the daughter board and Mel's board for easy disassembly and testing.  I've used it with absolutely no problems for almost 6 months at temps from over +100 F to well under -20 F.  Larry Bell

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Rule of thumb for overvoltage control is 4x the motor's rated voltage. You might eek out a little gain by going to 6x. Remember that at more than 3x overvoltage, you really need to have a dedicated circuit that regulates or throttles the current to the motor, otherwise, you will burn out the power transistors.           Mel Bartels

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Q  I'll be using a relay for voltage switching when slewing. Compared to processing time in the PC, it takes a large amount of time (always milliseconds) to perform the switching.

I was wondering that if, in this situation, scope.exe sends pulses to the motors then some steps will be lost as there is no power supply applied during this lapse of time.  This effect could be cumulative each time the switching takes place and finally degrades pointing precision. Rafael  6222

A.  Yes, this is bad, however there is a fix:  Increase HoldReps in config.dat to cover this time delay.  Mel Bartels  6226

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For the last nine months I have been driving my 6V motors at 24V straight  from Mel's board with good, reliable results. The only thing that I would advice if you go at 24V is that you install a big heat sink on the board's voltage regulator,    Juan Herrero 

+++

only for info:  I power the board since some years with round 36 Volt, (you can go up to 48-50 Volt, but-sure-be careful with this voltage) and use 12 Volt Nema (Decl.) and an real expensive 12 V stepper from "Nanotec" Munich) in Ra.  Never have problems.  8460

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I use 26V DC to supply my 6V stepper motors. No problem with overheating of motors, etc., as long as things are tuned properly. (Note: some use a different voltage supply to run the 5V votage regulator, but it should be able to handle 28V...but not too much more than that. Make sure the 5V regulator is heat sinked.   Tom Krajci    5499

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I implemented the overvoltage feature on my 12v/24v battery powered system.  I use a 5V relay. One side of the winding is connected to +5V, the other to pin 17. I placed a diode in parallel to the winding (diode's band towards 5V side) to short out back EMF. I set the HsOverVoltageControl parm to MaxDelay + 1. You can hear the relay click just before ramp-up and right after ramp-down. It works like a charm. I get smooth and quiet 12V tracking.  And reliable 24V slewing.   Juan Herrero  8405

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4X voltage is really a limit and I do not personally like to operate my circuit near the edge. I would recommend not to go over 3X voltage without some limitation. I found no advantage to run the motors with very high dc currents. The TIP-120 will have a tendency to heat and even if the motors display a little more torque, it is not necessary because around 2.5A, we normally have plenty of it.  An other consequence of higher current is vibration. The higher the current the higher the vibration. This vibration will eventually stall the motor at high speed. Of course, you can use Kajci's flywheel to absorb it, but why not control this vibration right from the start. There is an excellent explanation on motor operation in Mel's documentation where the bouncing effect or kick back is well explained. If you are interested, I recommend you these readings.                Jean-Charles Vachon

+++  

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  Is is safe to apply 36 V to Mel's PCB? Has anybody tried it?

A.  The 7805 are rated at 30V maximum and I personally do not recommend to operate components near their maximum values.  36V is definitely too high. I would also add an adequate heat sink on the 7805. I see no problem with the transistors or diodes. Again the TIP should have adequate heat sinks.   Jean-Charles Vachon

A.  I'm powering my PCB with a 12V DC-DC converter for 24V and was also worried about the 7805 getting hot. What I've done is to power that section of the board with a (12V) DC. Now the 7805 stays cool.  Don D'Egidio

+++

+++

We are using a 1.5 V stepper on 12 V with a current limiter to 2 A. Works great and gets motor rpm to more that 400 !!. Every thing heats up but does not get very Hot !!. Using a series resistor and current limiting circuits there should be no limit to the voltage u can use.. The power transistors should have a Vce rated at more that twice the operating voltage (Switching Inductive loads) and mounted with appropriate heat sinks .. And of course use optocouplers to isolate the pc from ur circuits .!!      sanath kumar

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While tinkering with the system, I noticed that the motors would run MUCH faster and quieter if I put my finger on the flywheel disk -- effectively increasing the drag on the motor.  At the same time I noticed, the motor current dropped from ~0.6A to 0.3A. 

I suspect, the motors are becoming unstable without friction.  I can't add more inertia to the shaft due to mechanical space limitations.  I considered adding a drag-brake mechanism, but it occurred to me that I might be able to achieve the same effect by lowering the overvoltage.

I experimented and found that at about 16V, I could run the motors almost 2X faster than on 12V and still have plenty of torque to prevent stalls.  The motors are stable and quiet at 16V but won't run wthout significant drag at 24V.                larry bell

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+++

If everything is right, you can achieve 10k halfsteps/sec with my unit with 4x overvoltage. For the 20k halfsteps/sec mentioned you are looking at 10x overvoltage. Many commercial units that offer these high speeds require 48 even 90 VDC input voltages. I made a conscious decision a long time ago to stay away from these voltages in the field. In an observatory setting they are safe enough with precaution, but out in the open, it makes me concerned.          Mel Bartels   2400

+++

the (current) limiting circuit will have no effect on most motors being used here unless they are being run with very - very high overvoltage. The inductance of a typical motor will not allow the current typically to get up to its ratings let alone above them.  (However the) circuit is perfect for overall protection and (is) one I would recommend.  5235    ...so again the only time the protective ckt is needed is for shorts. BUT I would agree in your situation, using very low volt motors, it WILL come into play as you are already many times overvolts (1.9v motors @ 13.6volts)!  I think most are using 5-6 and even 12V motors though.     Gary Myers5254

+++

Q.  I have half a Dozen PC power supplies and they come with +/- 12V, I was wondering if I could make some modifications and utilize the 24 volt potential.   James Lerch  6582

A.  What you can do is to tie the -12 to the gnd of the card, cut the track (there is a place to do this on the board) going to the regulator and tie the gnd of the power supply to this point (thus the 5v reg will only see 12V and won't run as hot), then tie the 12V supply to the supply input on the board thus providing 24V to the motors. This assumes there is a common gnd on the supply AND that the supply is an isolated one! If there are concerns on isolation then you will be better off (actually better off in all cases) to isolate the serial supply). If not isolated then you need to measure the voltage between the serial common of the computer and the common of this new supply (when not connected to anything!). It should read essentially 0V. If it reads more than this tie a 5-10K resistor between the 2 points and measure it again - this will load any earth capacitance there and show the true differential voltages. this should red 0. If not then you do not want to use that particular supply.

The current draw in this series arrangement should be less than the smallest of the 2 supplies. Also if you have a -5 and a +12 (or 24?!) you can make things even better - tie the -5 to gnd, tie the gnd of the supply to the output of the regulator thus providing 5V directly (remove the regulator), and tie the +12 or 24 to the supply -  best of both worlds even if tied to the AC mains.]   Gary Myers  6586 

+++

PARALLEL PORT:        http://www.bbastrodesigns.com/parallel.html    http://www.bbastrodesigns.com/5PortPin.jpg

http://www.epanorama.net/circuits/parallel_output.html 

Parallel port cable length - I've tested up to 100 feet without problems. If you do have problems, see if a separate power supply at the telescope location or power carried out separately via heavier cable, will help.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

+++

+++

My understanding is that the LPT pin usage closest is as follows:

2 altitude stepper motor - red

3 altitude stepper motor - green

4 altitude stepper motor - red/white

5 altitude stepper motor - green/white

6 azimuth stepper motor - red

7 azimuth stepper motor - green

8 azimuth stepper motor - red/white

9 azimuth stepper motor - green/white

10 handpad input (pulled to ground via 220 ohm resistor)

11 handpad input (pulled to ground via 220 ohm resistor)

12 handpad input (pulled to ground via 220 ohm resistor)

13 handpad input (pulled to ground via 220 ohm resistor)

18-25 ground

1 optional DC motor slow focus control out

14 optional DC motor slow focus control in

16 optional DC motor fast focus control out

17 optional DC motor fast focus control in

15 - PEC automatic synchronization signals 

  In other applications, pin 17 controls the overvoltage circuit.   Pawel

+++

I found that when I ran “TestParallellPort “ that the computer was giving me a high on all pins irrespective of whether I told it to be low or high through the software. Mel said try changing the LPT port from “888” to “956” and this fixed the problem. The port address on some laptops are like this as I understand it

+++

There is a table in BIOS that equates lpt number to port numbers. If you run the parallel port test from scope.exe, it will show you the table.  Mel Bartels

+++

I don't recall exactly but the parallel port sources very little current - something like 5-7 ma. Mel Bartels

+++

Never turn on the stepper power supply when scope.exe is not running.  The state of the parallel port is unknown and it could be set by the computer accidentally to power up the windings.   Mel Bartels

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Parallel port - 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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Parallel port pinouts : http://f5.grp.yahoofs.com/v1/cNBwP8CHg_sv8wXelG2bS71V9Z7E7dTEMpFCpO8vPPFfR38AjBz-Advax4421R5nji2ezpJCGqzJz1urvSzV9_57MxvGOvMOCgRNjQ/Parallel%20Port%20Data 

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PERIODIC ERROR CORRECTION:    Mel Bartels' Page  

          AutoPECsync          Analysis of PEC Data  Joe Garlitz' webpage

4. at your leisure, end guiding with (third) a handpad right mode key or the stoppage of guiding commands from the LX200 command channel   Mel Bartels

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Q.  Would someone please refresh my failed memory as to what the PEC display numbers mean? 

The "PEC" area, if PEC is on, shows the altitude and azimuth indexes and correction values in tenths of an arcsecond, respectively. In addition, if the auto-sync of altitude PEC or azimuth PEC is enabled, the PEC index at synch point is shown, and if an error, the PEC display is highlighted with the current selection color.   Mel Bartels 
http://www.bbastrodesigns.com/cot/operate_program_display.html
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PEC Synch is not handled during slews - the timing is too critical and I don't think it is of much use - there's no error correcting going on during slews.   Mel Bartels

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

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..polar alignment error will show as declination drift, while PE will show as right ascension drift.  Paul Lefevre 

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Periodic Error Correction works from the motor's viewpoint and provides for a table of 200 corrective values. Each value can be of any length, from 1 fullstep to many many fullsteps. So the PEC can cover a full rotation of the motor of 200 fullsteps up to a revolution of a gear further downstream that might take 30 minutes to rotate fully in normal tracking. I have found that 200 points, with interpolation in between, will adequately describe the PE. For corrections of larger scale such as a lump on the ground board, use one of the other corrective methods like alt-az or az-az or alt-alt or the pointing model. All you have to do is to start the PE at the same consistent point - it may be necessary to mark this point to a small angle of the motor revolution in the case of 200 fullsteps being covered all the way to merely marking a point on the ground board of the PE covers a significant fraction of a revolution. Mel Bartels

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FullstepsPerPECArray: This allows periodic correction for single through quad worms by tying the PEC sequence to an amount of fullsteps, not to a motor's single turn. Positive values in PEC.DAT indicate too much clockwise motion. Values are in tenths of an arc second.   Mel Bartels

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Q. . a 400-step motor with 50 X 1 gearbox attached to a 2" friction roller that directly turns the ALT and AZ circles.  Seems like the gearbox output would be the most critical and have most effect on the PEC measurement.    Mike Malowski

A.  Generally moves too slow and its effects are reduced by the gear ratio. If you have a 50:1 then the output error is reduced by 50x. So it is the input gear that turns at same speed of motor that is most important.  The PEC is usually applied to the reduction closest to the stepper. Further reductions downstream like the final roller drive or split ring rim also have PE, but the PE is so slowly changing that it is ignored by PEC routines. For instance, PEC in the reduction closest to the stepper might happen every minute or two, and PE in the main roller might happen once a night. So the PMC pointing model corrections are used to capture the main roller PE, and guiding with drift is also used. Mel Bartels  851

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

Q.   Is it correct that if PEC and alignment are perfect there would be no drift? mm

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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.    Mel Bartels

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Q.  If I have the HPDriftUpdate menu option turned off and have Guide+save (2/04 Guide + Save is no longer an option bd) enabled will anything be saved when trying to generate PEC data? Seems like the drift information is what is used to generate the PEC data and having drift calculation turned off would keep PEC generation from working at all.

A.  I think we are getting hung up on drift here. Drift is not critical to guiding efforts and can be dispensed with if you desire. Drift is essentially the drift in position over the time period between the beginning and ending of guiding. So if you start guiding at position '5' and after some time find yourself not at '5' but at '10' and the time was '100', then drift is 0.02.  

If you have drift update on, the 0.02 is adopted and used. If not, then nothing happens and presumably the small amount of drift that guiding 'discovered' will continue at the eyepiece.  Drift information is derived from the guiding information, not the other way around. Because periodic error usually dominates drift by an order of magnitude, it is important if you wish accurate drift to be calculated, to have PEC turned on, as this will force drift to be calculated as the difference in position over a PEC cycle, not merely the beginning and ending of guiding.

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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.

There are two methods to choose from: fixup an already generated PEC or generate a PEC from scratch  The PEC in use by scope.exe can be displayed by using the hotkey 'c'.

If you wish to save this PEC to PEC.DAT, answer yes.  

***STEP 1***

 To synchronize the PEC with the motors, use the handpaddle to move both motors to their respective synchronization angle, then select 'p' or pec on/off on the keyboard.  PEC is now synchronized with the motors and will remain synchronized unless the motors stall.

 ***STEP 2***

To generate PEC from scratch, or to to fixup an already generated PEC, put the hand paddle into guide+save mode (there is no longer a guide + save mode  bd), and guide until at least two high beeps and two medium beeps are heard, preferably until a low beep is heard, indicating that the guide array has been filled.  The higher pitched sound indicates each time the altitude motor crosses the synch point.  It must cross twice in order to generate a full motor rotation of data.  A medium pitched sound is used to indicate the azimuth motor's crossing of the synch point.  Multiple rotations of the motor will yield multiple PEC analysis files.  Better results may be obtained by focusing on only one axis, then repeating the entire procedure for the other axis.

 If using an equatorial telescope, or using an altazimuth telescope where one axis is moving very slowly (altitude axis when on the meridian for instance), then you will have to either misalign the scope or find another section of the sky where both motors are moving at a nice rate.

 ***STEP 3***

Use the 'u' and 'v' hotkeys to inspect the just completed guiding corrections.  If you wish the guiding corrections will be saved to PECALTxx.TXT or PECAZxx.TXT files, where 'xx' starts at '00' and is incremented for each file saved.  This allows you to build several iterations of guiding corrections in order to average them for a more accurate PEC.  In addition, the drift should shrink to zero as it is refined.    Use the 'e' and 'f' hotkeys to read in all the PECALTxx.TXT or PECAZxx.TXT files, average them, then display the results graphically, including how the pec will look if the averaged files are added in.     Use the 'L' hotkey to reload PEC.DAT.           

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Added prompting of individual PEC files to average. Before, all PECALTxx.TXT and PECAZxx.TXT files were averaged, now, you select which files to average.            Mel Bartels

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 In that case, you get to do something repulsive - purposefully and temporarily misalign your scope on the pole so as to induce declination
corrective action sufficient to generate a PEC curve.  Mel Bartels
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Q  The RA drive on this GEM is a series of good quality spur gears that combined total up to a non integer ratio.

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PECIxOffset.A, PECIxOffset.Z: index offsets of both axes between rotor position of 0 and synch point, for instance, if the current position coordinate is zero with the rotor in the up position, and you have 200 fullsteps for a PEC cycle, and if the PEC synch point occurs with the rotor in the down position, then the offset will be 100; leave at 0 until PEC is turned on and synchronized, at which point let the program determine these values   Mel Bartels

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Q.   Are the ALTAZEC and PMC corrections tied to the PEC index?

A.  No, they are only tied to the current altitude and azimuth values. PEC is tied to some repetitive # of  fullsteps, because the most important periodic errors come from the worm or reduction that the stepper drive shaft is attached to. The ALTAZEC and ALTALTEC and PMC are corrective values to be applied based on altitude and azimuth.             Mel Bartels

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An autoguider is great for doing the corrections to build a PEC table.  Marty Niemi

....Or, (maybe) the stepper motors are dropping steps.

Is there a way to observe the stepper shafts? If so, put a mark on them, move the steppers to a handy 'zero reference point', turn on the PEC option in the software (tracking is off at this point), turn on tracking, make many slews, turn off tracking, use the software's Move to Zero PEC option, and see if your RA shaft is at the zero reference point...where it's supposed to be.             Tom Krajci     6168

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Q.  As I understand it, Scope.exe will fix only ONE instance of Periodic Error for each axis (this is correct, yes?). James Lerch 11128

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As I understand it, Scope.exe will fix only ONE instance of Periodic Error for each axis. In Andy's example, an off-centered worm wheel, could be fixed as long as he had a perfectly centered and true worm shaft attached to the stepper motor. In addition, if Andy had more than one reduction stage, each stage would have to be perfect as well.

Q  As I understand it, I can do a Guide/Save mode on the fly and, so long as the motor doesn't stall, PEC will stay sync'd with where I left it (sort of like the Losmandy drive). I am not worried about coordinate resets since my plan is to center and focus the object then run the PEC train right before I image. This would be done for every object. Also, this is a GEM so I only want to work with the RA axis.

A.  Mark your worm gear with an "index" mark. The position of the worm is totally arbitrary. Mark it where the mark can line up with something so you can use the handpaddle and slew RA till the worm lines up again with the mark. Then turn PEC OFF, and then turn PEC back ON. This will tell scope to sync the start of the PEC cycle with the start of your arbitrary index mark. In the future, if you re-sync the worm to this mark you will not have to re-train PEC to use the pec.dat file that you will build.  

Building the PEC.dat file is a 4 part process.  The first is to use Guide+save mode as you described.  (there is no longer a guide+save mode  bd)

The second part is to extract the data from the guideaz.dat file that was built while in guide+save mode.  

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Also, if you use an auto-guider to train your PEC, do not instruct it to be overly aggressive. I use 5 asecs/sec guide speed and tell it to ignore any movement less than 0.5", however if seeing is really bad, that might need to be increased. If you have some really fast, deep errors, I can see where your might need to increase the guide speed.    Brian Sherrod

AUTOPECSYNC:

PLANETARIUM PROGRAMS:              http://www.bbastrodesigns.com//operate_interfacing.html 

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Q.  In Guide do I choose 'alt-az' in the Scope Control Box when using it with Scope.exe?

A.  ...when using AltAz, Guide doesn't send anything to any serial port. Instead, it creates a file, 'slew.dat', containing assorted data such as the selected RA/dec, its alt/az, rate of field rotation, etc. (expressed as cubic polynomials in time).  When the 'AltAz' radio button is selected in Guide, the com port selection is ignored.  Mel's program is capable of interpreting LX200 commands. Set Guide's Scope Control dialog to work as an LX200, rather than in AltAz style, and it'll send LX200 data out over the selected serial port. 

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I went into the telescope configuration setup in Carte de Ciel and played around with the various timing values until I got some that worked. In case anyone else has this trouble Carte stores them in Scope.ini in its directory and I finally got the following values to work

[lx200]
name=LX200
read_interval=1000
comport=COM2
baud=9600
databits=8
parity=N
stopbits=1
timeout=1000
model=0
hpp=1
AltAz=0
AlwaysVisible=0
SwapNS=0
SwapEW=0
inttimeout=500                        Tim Scott

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Can you find a setting in StarryNight pro to turn down the aggressiveness of contacting scope.exe? If the contact is too fast and too often, then scope.exe and delays in the serial processing on both machines may cause StarryNight to see that a coordinate was not returned. Updating coordinates once a second is more than adequate.   10403
Mel Bartels

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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 unacceptable. 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.

I suggest letting Megastar and scope.exe interact via the lx200 serial port. Let scope.exe send back equatorial positions accurate to arcsecond, and tell Megastar that scope.exe is a lx200 scope, and tell Megastar the latitude and longitude so that it can do any horizon displays that are necessary.

That way you avoid the fundamental problem of scope.exe returning corrected encoder counts that can only resolve to a large number of arcminutes because they are limited in overall range.  Mel Bartels3557

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POINTING ACCURACY:    see Analysis  and  Periodic Error Correction     http://www.bbastrodesigns.com/operate_local_finding.html

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

I consider 1 arcminute RMS pointing across the sky, with 1 arcsec localized pointing from known offset positions, a truly admirable and final goal for amateurs. The best rigorous result that I've heard of (that means that the survey is spread out across the sky, that the estimation is done with measuring devices of some sort and not guessed at with the eye, and that all data points are considered - none rejected to make results look better), is with a Meade 12" using TheSky and TPoint on a permanent observatory mount, the result was something around 1/2 arcminute RMS.

There are a whole host of pointing issues when considering 1 arcsecond RMS pointing across the sky that the software does not address, many of them with the coordinate values themselves.                   Mel Bartels

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Using these EC, Tom Krajci with a *portable* mount is able to do 30 arcsecond rms with horizon to horizon slews. (my software contains  analysis functions to determine rms pointing) This contrasts favorably with amateurs using permanently mounted scopes and TPoint also achieving 30" rms h-h slewing. Scope.exe does not handle the arcsecond range of EC that TPoint and observatory scopes will do. I do not regard this as necessary for amateurs. If it becomes necessary I will add arcsecond EC for h-h slews.        Mel Bartels

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A    .08 deg error ~ 5 arcminutes.  That's about ballpark for what people are getting today without advanced methods such as the error correction to push the error down a magnitude.  The error can come from a variety of sources. In addition to what you mention, don't forget tube droop and mechanical flexing, along with optical axis changes. Mel Bartels

A.  I do remember writing and posting a scroll file test.scr that basically slewed the scope all over the place for about 30-40 minutes and then returned it to the same place to determine if there was any slippage in a system. The test does not test overall pointing accuracy around the sky which you can only do by going into analysis mode and analysing stars all over the sky.  If you are using a roller driven drive rather than directly geared drive then the results you have achieved are great. 

Don't remember anybody else posting results. While this slippage appears large, if you do an equat reset on a known object every now and then it zeros any slippage that may have occurred and accurate pointing can still be achieved.  With a fixed gear system and no slippage you should get no error (or only as accurately as you can measure the error) as the scope away from and then returns to the same spot and it doesn't matter if your step sizes are a bit inaccurate as it steps the same number of steps to move away as it does to return. The only error will be any backlash you have not compensated for correctly. And yes backlash works for both slewing and microstepping.   Andy  Martyn

whenever I 'miss' an object, I usually slew back to where I started.  This checks for a number of things including slippage and motor stalling.    Mel Bartels

POINTING MODEL CORRECTIONS:

Q.  Are the PMC corrections implemented only using the Z1,Z2 and Z3 values, or does/will PMC allow coefficients which will vary with time/scope position?  I.E. varying radius drive rollers/sectors.

A. The PMC is a general all-sky pointing correction routine. So you have your errors

backlash
PEC
refraction
possibly drift
Z1 (axis misalign)
Z2 (az offset)
Z3 (alt offset)

(working on these two now)
rocker base
altitude eccentricity (tube flexure and so forth)

then comes the all sky PMC which calls for you to take an analysis file composed of points all over the sky in a grid like fashion; basically it works by adjusting your position by giving more weight to the closest PMC points to your current position  Mel Bartels

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POLAR ALIGNMENT:        http://www.bbastrodesigns.com/operate_equat_startup.html 

5-2-06  Totally revised Polar Alignment Routine.  Now uses only two stars.  I've
also attached a draft of a monograph describing the solution.

Q.  Can you shortly point us to description how the new polar alignment routine works??

If your polar alignment is off by 10 arcminutes, then I'd expect goto pointing errors to be of the same magnitude.  Mel Bartels

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Three Star Polar Alignment Procedure The Three Star Polar Alignment procedure does not depend upon local latitude or local sidereal time so neither of these need to be set in the config.dat file. The values for Azimuth and Declination are also not needed so the four limit values in config.dat can be set to 0.0 and Az/Dec ignored or set as normally used.

The mount should be adjusted so the polar axis is roughly polar aligned. Start scope.exe with startup option 1, select equatorial alignment. As scope.exe starts up with Current Alt/Az set to the current values the last time config.dat was saved, you must either have the scope pointing in that orientation or pointed at a star selected from the databases, followed by a ResetEquatorial.

If the handpad LeftKey is to be used to step through the alignment procedure, select menu option Handpad/SelectHPMode/ Polar Alignment BEFORE starting the polar alignment procedure.

Note In this mode, the slew distance limit warning is turned off. If the polar alignment procedure is aborted, the Handpad Mode should be changed manually. Three Star Polar is initiated by menu option Init/PolarAlign or by hotkey '*'.

Note If the polar alignment procedure is aborted, it can only be restarted via the menu option. 

Upon starting, the user will be asked to select three stars from the datafiles. The Star 1 can be in the east (or west) and about 45 degrees elevation. Star 2 and Star 3 can be in the northeast and south- east (or northwest and southwest) and at about 10 - 15 degrees elevation Tracking will be turned on. The user should then center Star 1 in the eyepiece manually and/or using the handpad Up/Down - CW/CCW buttons. When Star 1 is centered, hotkey '*' or Handpad LeftKey should be pressed. You cannot use a star that's almost due East or West for Star 3. Try with Pollux or Castor as Star 1 and pick stars in S or SW for Star 3.

The scope will now slew to the epoch 2000.0 position of Star 2. If the polar axis is correctly set, the star will now appear in the eyepiece. If it isn't, it should be positioned using the handpad Up/Down - CW/CCW buttons. Reset should NOT be pressed. When Star 2 is centered, hotkey '*' or Handpad Leftkey should be pressed.

The scope will now slew to a position calculated from the difference between the apparent position and epoch 2000.0 position of Star 2. The user should then physically move the polar axis up/down and east/west until Star 3 is centered in the eyepiece. When Star 3 is centered, hotkey '*' or Handpad Leftkey should be pressed. The scope will now slew back to the epoch 2000.0 position of Star 1, which should now be centered in the eyepiece. Pressing hotkey '*' or handpad LeftKey will give the user the choice of repeating the process or quitting. If a repeat is selected, the same three stars will be used for the next pass.   Don Ware

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(The first time) I manually pointed in the general direction of Star 1 and used the handpad to center. A ResetEquatorial happens automatically when you hotkey * or HandpadLeft.  

To work with the May 6 version, I set the declination arm level with scope on the East side and pointing to Polaris. Set equatorial to DEC = 90, RA = local sidereal time. This gives Alt = 90, Az = 0. Then save config.dat. The next time you start up, your equatorial coordinates will be DEC = 90 and RA = local sidereal time. Scope knows where it is and will slew towards Star 1 ok.  

If you want to align using eastern stars, do a Manual GEMFlip. Swing scope to West side to pier. Equatorial coordinates will still be DEC = 90, RA = local sidereal time, but now Alt = 90, Az = 180.  If you ever save config.dat again, make sure equatorial coordinates are as above before saving.   Don Ware

If the polar alignment routine is aborted in the middle of the sequence of going from Star 1 to 2 to 3 and then back to 1, you cannot restart it using hotkey '*'. You must restart using Menu/Init/Polar Alignment. The reason for this is that the routine is divided into a series of steps and hotkey '*' goes to the next step after you stopped the previous time, not back to the beginning. This is true even if you're using the handpad to do the stepping. Of course you will have to rechoose you're three stars when you restart.  You can always define one of the user defined hotkeys F9-F12 as Menu/Init/Polar Aligment. This will always start at the beginning.   Don Ware

-  when polar aligning, during the time you're slewing from Star1 to Star2, centering Star2 and slewing to Star3, the scope is tracking around a misaligned polar axis . The longer that process takes, the poorer the alignment will be after adjusting Alt/Az of the mount. I almost always do a second pass.      Don Ware

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Q.  Does this feature allow the datafiles to be placed in directories, ie. Messier dat files a Messier directory, NGC files in NGC directory etc., so that the "D" hotkey will pull up a listing of directories and then selecting a directory will pull up the dat files in that directory?

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END OF NEW POLAR ALIGNMENT PROCEDURE

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BEGINNING OF POSTS ON OLD ALIGNMENT PROCEDURE - SCOPE.EXE PRIOR TO 3/26/03

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You can improve the polar alignment as follows:

1. center a star close to the meridian then go to a star on the celestial equator about 30 degrees above the horizon
2. adjust telescope polar axis until star is centered
3. go back to first star and recenter
4. repeat #2 as desired
That should do it.    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).   Mel Bartels

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Further, if you don't know if you are polar aligned, you can do the 2 inits, look at the init values via the 'i' key, and reposition your mount (for instance, a latitude of 89 degrees and a small hour angle error indicates that you are 1 degree too low), starting over with either 'adopt equat mount' if you are satisfied that you have the alignment, or go through another series of 2 inits to look at the init values once again.  Mel Bartels

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POWER SUPPLY

Q.  Is it a problem to use a 14V battery and not 12V as stated in Mels circuit-diagram?

A.  It is not a problem, in fact, many 12 volt batteries actually output 13.7 volts. Mel Bartels  10038

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Q.  If the circuit is OFF it is 11.70V or something, but when the circuit is ON it drops to about 7V. Is this a indication that my batteries are not powerful enough?

A.  The voltage drop is caused by your batteries not being able to supply sufficient current. You can increase the available current by putting more batteries in parallel, ie having two series of 8 batteries in parallel will double the available current. A better alternative is to use something that can supply more current like a car battery. Andy Martyn   9985

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Q.  I am using 0.4A 12V steppers to move my 20" scope; the power being supplied by a AT computer PSU. The steppers are pretty much on the limit as far as getting reasonable slew speed goes. I would like to try 24 V with these but haven't found a suitable power supply. 

A.  Take a look at the data sheet for the LM350 posted on the National Semiconductor site, there is a current limiting variable voltage power supply among the examples which uses a MJ4502 PNP pass transistor and an LM301. The supply when built with a suitable transformer will supply around 2 to 35V @5A.  Jay LeBlanc

A.  I use two car battery chargers in series with no ill effect.    Juan Herrero

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Q. Has anyone taken a power supply from an old junk computer to use to power Mel's circuit, rather than buying one?

A.  ...a garden variety ATX power supply should have plenty of current capability (you can even buy them surplus pretty cheap - I got one from MECI for only $10 plus shipping). The only thing you need to be aware of is there's a minimum load spec, usually 5-10% of the full rated current on the 5V supply. If you try to power one up with no load, it won't work   Just figure out a resistor to put on one of the 5V outputs that will give a current that's high enough. You might have to experiment if you can't find the documentation on the supply (and make sure the resistor wattage is high enough).  I'm planning on using some resistor rope as anti dew heating for the focuser and secondary mirror so the mirror and eyepiece don't fog (a big problem here in Florida during the very humid summer nights) to put me over the minimum load requirement. All in all, it's a very cheap, perfectly suitable power solution.  Steve Rivet   1556

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So I changed to a 22v/12v/5v switching power supply, fed the motors with 22v, removed the 7805 and fed the logic with 5v. The encoders and fans at the mirror run off the 12v supply. After many hours now, so far so good. No heat and no flakes. Ben Davies

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Q.  what kind of battery set-ups are folks using in the field?

A.  34 amp hr marine grade (fishing) battery. It has a reserve of 41 amp hours.  Inverter (150 watt) for the laptop and 12 volts for the pcb. It will run easily for 2 nights.  The battery was purchased at Walmart for ~US$30.   Lenord Stage  1500

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If you can find an old fotocopier machine, they have very stable, heavy duty power supplies with lots of power.  Mine produces 18 volt 9 amps (witch i do only need during 0.5 seconds in the ramp up or down. when slewing or microstepping, the consumption is about 2 amps with both motors connected.  I know this sounds a lot but i am overpowering the motors 5 times nominal voltage to achieve high speed slews. Johan Coussens  9128 

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I think there's a high probability you'll damage the PC's motherboard. (tapping in to the desktop's power supply) You can buy surplus PC power supplies for less than $20 at places like Jameco, H&R, etc. Having a separate supply would isolate any spikes from the motherboard's sensitive electronics. Steve Rivet  9125

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PC power supplies have several outputs. 5v, +12v, and -12v and some may have other voltages for the new processors. The 5v side usually supplies quite a bit of current, as most of the pc motherboard runs on it. the 12v sections of the power supply have a very low current rating. At the very least, you will keep locking up your pc during slews. At the most, the power supply will go into overcurrent shut down or smoke.

I power my scope electronics from an old computer power supply, however, it was quite beefy in the 12 v department. Also, it's powering the scope electronics and motors alone. It's a bit bulky with all the gizmos hooked up, but works fine.

However, most pc's have quite a bit of excess room inside the case. That should allow you to mount your scope electronics in it and also a second 'scope' power supply.

One point is, you'll have enough of a challenge getting the system to work  properly without having to worry about power supply glitches and computer  lockups. Save yourself some trouble.   Bob Norgard  9126

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PC supplies generally have hordes of protection features and it's hard to damage them - they also make it hard to damage the PC electronics they were designed power, and that brings up another problem. PC power supplies generally require a 10% minimum load (10% of the total maximum rated current on the 5V outputs). This little quirk had me convinced I had received a bad supply from a surplus company until one of the engineers here at work pointed out this feature.  If that current draw is not present, the power supply won't start up - it won't damage the power supply, but it will shut itself down by disabling all of the outputs. Mel's board only draws a few mA, so that's not enough. You have to create this minimum load, how much depends on the max 5V rated load. I solved this problem by connecting the 5V output to enough anti dew ropes to get over the min threshold - the current draw of Mel's board is low enough that it won't be noticeable compared to the dew ropes. If you don't want to hook up an anti dew system, you can just hook up a power resistor to draw enough current to get you over the threshold. You can hook the load to any of the 5V supplies (12V might even work, but I haven't tried that). Either the resistor or the dew ropes (the same thing really) are purely resistive, steady loads that won't generate noise and upset the electronics on Mel's board. Steve Rivet    8456

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All of the electronics in a laptop use voltages much lower than 10V. The battery voltage is regulated down to a level usable by the electronics; if the battery voltage is a little higher, the regulators can still handle it - there is a safety margin built in. As long as you stay below the charger voltage, you should be OK. However, the charger voltage does need to be somewhat higher than the nominal battery voltage if you want to charge the battery in a reasonable amount of time. If the battery voltage equals the charger voltage, you will never really charge the battery.    Steve Rivet  7316

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I try to run the laptops and the pcb off the same battery. I have three different way of doing so:

1. 1 splice into the cable that powers the laptop from AC with 3 db-9 connectors. One goes to the the cord and plug that attaches to the laptop.  The second to the ac power line, after the voltage converter. The third to a 2 wire line to the battery, with clips to attach it to the battery. This allows the ac converter or the battery to be used and is less intrusive.

2. If the plug to the laptop is available from radio shack, I just use one of their plugs and solder a 2 line cable to the battery and the new plug.  This does not always work though.

3. If I have a dead battery to the laptop, I take out the cells of the battery pack and solder in 2 wires (where they need to go) inside the battery pack where the batteries were. Then I solder two wires to a plug type that I have a male and female for. The female goes inside the battery pack where the old cells were and sticks out the side. (I drill a small hole in the side of the old battery pack housing for this). The other plug gets two wires and 2 clips to attach to the larger pcb battery 

I have found that this third arrangement works best when the factory ac converter supplies more than 15 volts to the laptop. The first two work when the ac converter supplies less than 15 volts to the laptop.

Most of the factory battery packs I have seen only supply 12 or 13 volts to the laptop making them easily usable from a 12 volt marine grade battery. Lenord Stage  6669

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I installed 2 4700 uf caps right on the voltage rail on Mel's card. (Used the space intended for the derotation components).  This reduced the noise to 1/10 volt on the 13 volt rail.  My slews got faster and the stepper noise was slightly less.  Bob Nielson

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Q.  My manual slewing via the handpad is fine. I took a lot of time fine tuning config.dat to get halfsteps and microsteps just right. When I go out to use the system I carefully polar align, reset to eqat on a star then pick a nearby star and select "move to eqatorial" the motors the accelerate until a stall occurs and I lose alignment.

A. This can be caused by a power supply that can not provide enough current to drive two motors at the same time. It works ok for handpad because only one motor is being driven. But a slew will drive both motors at the same time. If you have a volt meter measure the DC voltage at the supply while the slew is in progress if you see the voltage drop by a few volts then that is your problem. It can also be caused by too small and too long of a wire from the main supply. Again you can measure the voltage drop from on end of the supply wire to the other. If you see more than a volt then that is your problem.    Dale Eason

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PROGRAM DISPLAY:              http://www.bbastrodesigns.com/operate_program_display_servo.html 

Q  I just executed scope.exe and hit 't' key to switch tracking on. Then I used the handpad to center some star through the finder, a few numbers appeared just below the line of AZEC, AAEC, ZZEC and PMC.  What do they mean?

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QUARTER STEP CORRECTION:

Don't forget to make the current compensation before making the QSC one. Mel Bartels

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I did not realise that QSC acted like the other correction factors. I had visions that it actually effected the PWM array values to physically alter the microstep position. So basically when the scope is tracking at a constant rate, the software is subtly increasing or decreasing the microstep rate to account for varying microstep sizes over the four coils and thus the scope tracks across the sky at a constant rate.  Andy Martyn

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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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Q.  Should I attempt to correct with QuarterStepCorrection before doing the microstep ratio adjust ?

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The "Ms" area shows ....... the quarter step correction for altitude and azimuth motors in decimal fullsteps.    Mel Bartels  4201

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for stepper motors, physical variations in the quarterstep spacings over the sequence of windings (called QSC for QuarterStepCorrection)

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since QSC is applied externally to the PWMs, you can tune the PWMs after QSC.  However, it is likely that the quarter step QSC correction will need to be tweaked slightly.         Mel Bartels

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Q.  the actual spacing between microsteps or fullsteps does not change when you apply QSC but the program slows or speeds up the steps so that the rotational speed stays constant? So after I apply QSC and look at the positions of the microsteps projected by the laser on my piece of paper on the wall I will see that the actual microstep positions have not changed?

A.  Exactly, qsc will change nothing when tuning individual microsteps.  Mel Bartels 6736

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Q.  My midpoint PWM at 100:100 puts the laser pointer about 30% off from the true half way point between full steps. So the laser dot first moves through the longer distance half step and then slows down as it moves through the tighter spaced second half  step.

A.  That might be tolerable at the eyepiece. You might give it a go and see if you need to tune up performance or decide that the 30% variance is geared down so much that it is not visible by the time it gets to the eyepiece.

30% is about the limit of what I would reasonably expect to hide by the gear down ratio.

Better than setting ms speed to 1 arcsec/second is to use the 2 motor track and set a tracking rate of say 1. That's a bit more consistent as basically all other distractions are turned off in this tracking routine.    Mel Bartels

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you can use the quarter step correction (QSC) to fix microstep positioning, particularly if the microsteps are fairly evenly spaced but yet tend to bunch up such that the middle microstep comes early or late.  

QSC is really meant to fix smoothly varying stepper motor errors over the sequence of 4 repeating windings. For instance, you might find that the first microstep sequence has its midpoint early while the second microstep sequence has its midpoint late.

If you find that the QSC values are pretty much the same over all 4 windings, then it is clearer to adjust the PWM[] A : B values and turn off QSC.

QSC started with Tom Krajci's observation of what many of us had seen in certain steppers, namely that the halfsteps were not always evenly spaced, and his further observations that this extended down into the quarter step level.      Mel Bartels   4255

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Q.  Isn't this exactly what I need to correct the over long steps on the motors I wrote in about? Certainly sound like it. If I've got two short steps (a0 and b0) and two long steps (c0 and d0) should I be able to apply this to the shorter or longer steps to correct it? The 400 step motor may be a cheapo but the Vexta wasn't and it was used for microstepping but driven off a commercial Parker Compumotor type drive unit originally. If I'm getting 2.84" 2.84" on the first two full steps and 3.6" and 3.5" on the last two (400 step) can the QSC correct for that disparity. That is at a 200" radius. The Vexta was 5.8", 6.0", 6.5" and 6.6"

A.  Yes, this is exactly why the QSC is meant for.   the corrective factor will speed up the motor during the shorter steps and slow down the motor during the longer steps to make an even velocity.      Mel Bartels  6743

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Next you work out QSC which is worthwhile if you see large differences between halfstep sizes. First point the laser at the paper on the wall for fullstep position a0 and make a mark. Advance the motor through 4 fullsteps until you get back to a0. Divide the distance between the two marks equally into 16 equal distances which gives you the ideal quarter step sizes. A point to note is that because the motor is moving a few degrees over the four steps and the laser is projecting onto a flat surface you will small tangential errors. You can adjust the marks to allow for this error, or make an adjustment when you are working out your QSC values.

Now just step through the microsteps and mark on the paper where the laser says the quarter steps are.

Calculating the QSC values is then just a matter of measuring the difference between the measured quarter mark and the ideal quarter mark and then dividing it by the fullstep distance. For example if the distance covered by the 4 fullsteps is 600mm then the full step size is 150mm and the differences for the first 4 quarter steps are 0 (the first value is always 0), +10, +5, and -10, then the QSC values are 0, 0.067, 0.033, and -0.067.

This completes the process for the azimuth motor...You now plug the altitude motor into the altitude output and repeat the whole process again for the altitude motor.   Andy Martyn  7858

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QSC_a0 Alt : Az      Lefthand side is altitude/declination, righthand side is azimuth/right ascension    Mel Bartels

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Q.  Can I create separate QSC tables for the different steppers ?? If so, what is the format ???

ie  from http://www.bbastrodesigns.com/cot/config.html Optional variables: QSC_..., which stands for QuarterStepCorrection: the '_a' through '_d' indicate the winding, and the extra '2' indicates the intermediate halfstep; enter corrective values in fullsteps, for instance, if the motor moves too far for the 'a' winding by 0.1 fullstep halfway through its range, and no other corrective actions are required, here is what the entries will look like for the 'a' winding (for windings 'b' through 'd', duplicate these entries, replacing the 'a' with the winding

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Step by step:

1.- Take the full length of the four steps and divide it in 16 equal segments. These are the ideal positions. Make this for AR/AZ motor and for ALT/DEC motor.
2.- Take the difference of the real data to each ideal data (you have 16 points per motor).
3.- Divide that difference by the MEAN length of a step (in ALT/DEC is 668 / 4 and in AR/AZ is 661 / 4). This result is what is needed to input in  SC_a0 x:y values. x for ALT/DEC and y for AR/AZ.

There are more questions, not directly related with the maths mentioned.

I realized that "tangent" errors may accumulate. What we are really measuring are angles, and a projection to a wall is a mix with tangents.  I've calculated that on a 5 meters distance there is a very little error with 1 step (in a 200 steps/rev motor). But four steps give an important error (4.5 mm in 661 mm). I corrected the data given in my mail to make the QSC adjustments, but I choose to send raw data to simplify and get "concepts".

With these corrections and the concepts Mel and Tom gave, my QSC correction is:

;Quarter Step Correction ALT/DEC : AZ/AR
QSC_a0 0.000 : 0.000
QSC_a1 0.015 : -0.031
QSC_a2 0.025 : -0.025
QSC_a3 -0.002 : -0.037
QSC_b0 -0.024 : -0.019
QSC_b1 -0.036 : -0.035
QSC_b2 -0.039 : -0.033
QSC_b3 -0.040 : -0.040
QSC_c0 -0.025 : -0.029
QSC_c1 0.003 : -0.034
QSC_c2 0.008 : -0.033
QSC_c3 -0.009 : -0.035
QSC_d0 -0.021 : -0.038
QSC_d1 -0.012 : -0.026
QSC_d2 -0.003 : -0.015
QSC_d3 -0.022 : -0.007                       jprieto   2853

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I have gotten my 20 microsteps even and have been trying to apply the QSC to get the full steps the same size. I have (finally) figured out that the correction value is derived from:

1. measure the actual distance of four full steps from a0 to a0. Divide that by 4 to get the ideal full step size and by 4 again to get the ideal quarter steps. While getting the 4 full steps, mark where each 5th microstep falls giving you 16 measured values.

2. divide the measured qs by the ideal qs to get a positive or negative result. Divide that number by the ideal full step size and the result is what is entered into the QSC table. The measurements are all from a0 to whatever quarter step is being measured, a0 to b15, a0 to d10, etc.
What I have in my table is entered as 
QSC_a0 0.000 : 0.000
QSC_a1 -0.023 : -0.058
QSC_a2 -0.091 : -0.023
and so on with a single space between each number or colon. I placed the list in the microstepping section of config.dat. Lenny Shaffer7362

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QSC or quarter step correction works the same as the other error correcting factors. They are applied to the motor position to arrive at a sky or celestial position. So when you advance the motors ahead and behind discreet microsteps, you will not see the error corrections applied, but when utilizing the tracking and goto, you will see the error corrections applied. QSC is linearly interpolated, as are most of the other error correcting values, except for the PMC Pointing Model Correction, which is computed with a weighted factor.

For example, if the accumulated motor microsteps is 1,000,000, and the fullstep size is 5 arcseconds, and there are 40 microsteps per fullstep, thn the raw motor position is 1,000,000*(5/40) = 125,000 arcseconds, or 34.7222 degrees. If we are on the first quarter step of the sequence (winding A, microstep #10), and the corrective value is 0.1, then the corrective value is 0.1 fullsteps * 5 arcseconds/fullstep or 0.5 arcseconds. So the  corrected position is 125,000.5 arcseconds or 34.7224 degrees.

The effect while watching the motor will be to smooth out its motion.  Compared to an uncorrected motion, the motor will appear to speed up or slow down slightly.     Mel Bartels    6729

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REFRACTION:      Atmospheric refraction

Airmass is the number of atmospheres that the telescope is looking through. At zenith, the Airmass will be 1, for instance. CCD imagers may have a particular airmass (say 3) that they will not image through. For those looking at primary equatorial coordinate side of scope.exe, the zenith angle may not be immediately obvious, hence, the Airmass value is calculated and displayed now for you.     Mel Bartels

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REMOTE TELESCOPE OPERATION:

Q.  Anyone using Scope.exe for unattended remote operation?

The real question is not cable management, as I think this is solved by a little planning, but instead, it is the difference between computer control and remote control. Computer control means that you can reach over, or at least dash out of your bedroom to fix a problem. Remote control means every contingency must be planned for and feedback from the site like weather and cloud cover becomes important.

Internet control is no biggie - I had a PERL script someone wrote that takes email messages and outputs LX200 serial port commands, so the interfacing from the network view is straightforward.

I would like to see more interest in this arena, and I am sure that this will gradually occur as the number of remote sites increase.                    Mel

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RESET EQUATORIAL:

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

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

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"R" leaves all init data untouched.  You basically tell the program that a specific set of input coordinates corresponds to the center of your FOV. It greatly enhances local finding but does nothing for global pointing accuracy. I use it all the time while observing and also in all my scroll files after each object entry as a quick and dirty pointing improvement. Practically speaking, to observe M57, I would for example point the scope to Vega, center it, do a "r" and then move to M57. As mentioned all this can be conveniently included in a scroll file.  Berthold Hamburger

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..select equatorial option (for an equatorial mount) at program startup the scope will track accurately for any position in the sky, and, if the laptop's time and date is accurately set and the longitude value in the config.dat file accurately set then the scope will also slew accurately but most likely these values will not be exactly accurate, so to refine the positioning: 

center an object in the scope

enter object's coordinates via one of the data files, or manually if necessary

then do a reset to equat coordinates to inform the software where you are pointed

remember to never do any initializations at any time because it will confuse the original equatorial initializations at program startup time     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 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

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Q.  what is the difference between 'initializing' and 'synchronizing'???

A.  Well, this can be confusing. Initializing means building a relationship between the telescope's coordinates and the celestial sphere's coordinates. Because the celestial sphere is two dimensional, we need two points to define this relationship. Each point carries information on the celestial coordinates and telescope coordinates and what time this connection between the two coordinate systems was made (of course, in sidereal or star time). 

Once we have this relationship, we can calculate coordinates in one system given coordinates in the other. For instance, celestial coordinates are RA 99:99:99 Dec 99:99 (9 means some digit) so what should altitude and azimuth be? Once we have calculated altitude and azimuth, subtracted out the current altitude and azimuth, we now have the distances we should command the motors to move.

Now let's say that we have relationship built, that is, we have initialized the telescope to the sky, and we aim the telescope at a star, but the star is to one side. This means that both coordinate systems are equivalently incorrect, and we need to adjust them. Typically, we know what the celestial coordinate system ought to be since we can look up the star's position. We then change the telescope's coordinate system to make. We do NOT change the alignment between the two coordinate systems: instead we merely true up the numbers of one coordinate system based on what the other system should be. This is called synchronizing the  telescope to the sky. In my program, I call it 'reset to equatorial coordinates' since we are resetting the telescope's coordinates to that of the sky's.   Mel Bartels9870

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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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SCROLL FILES:     http://www.bbastrodesigns.com/operate_scroll.html     http://www.bbastrodesigns.com/operate_grandtour.html

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if you put    ‘auto_scroll’     at the start of your scroll file the scroll file will be stepped through automatically as soon as each step is finished.  Of course any motion limit hits or abnormally long slews beyond the MoveHsMsgDeg limit (default is 10 deg) will cause a message to appear interrupting the automatic step through.               Mel Bartels

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4/27/03     Fixed grandtour so that it will use datafiles not in scope.exe's file directory Remember you can run scope.exe with scroll file autostart, for example: ”scope.exe -x init35.scr”         mb

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Q.  Is it possible to add a pause command to the (scroll file) script language?  e.g. 'pause hh.mm.ss'

A.  Yes, repeat the equatorial coordinates you are currently at and give it a time delay, ie

o 0 0 0 0 0 0 30 pause30sec

which says to do offset equatorial over 30 seconds with no change in equatorial coordinates (the pause30sec is merely a comment that will
appear on the program display)     Mel Bartels

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A.  The program decodes your input and then opens the appropriate .dat file to look for the input object. If the object isn't in one of the files, entering ** will allow you to enter epoch 2000 data and name for a comet or whatever.  Perhaps I could allow entering other file names after the ** prompt in addition to epoch 2000 data. Let me work on that.  Don Ware

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SERIAL PORT:           see Modem to Modem connection

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Scope.exe expects no flow control – plain bare 3 wire stuff. Mel Bartels

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(scope) works successfully with 9600 baud, n,8,1, no flow control.  Mel Bartels

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Do not use xon/xoff. If scope.exe has trouble reading values returned by the encoder interface box, it will tell you.

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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SERVO          http://www.bbastrodesigns.com/NewProductAnnouncement.html 

SIDEROSTAT:

On the split ring mounts, you can set  Siderostat 1 in config.dat to allow the scope to take advantage of the split ring design to move below the pole without rotating the RA 180 degrees. This is important for supernova hunters in the higher latitudes who want to gain an advantage on surveys that operate closer to the equator! Mel Bartels

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Default is to not allow this. Turn on the siderostat option in config.dat if you wish to go past the (meridian) without rotating the base 180 degrees.     Mel Bartels

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The siderostat option works if you set the AzLowLimit and AzHighLimit to approximately 90 and 270. This tells the program when to allow the scope to travel past the pole. Do not use the GEM flip with it.

This option was originally developed for a guy in Connecticut who had a 27" telescope pointed downward to the SE into a mirror that was angled around the sky. Later others who had split ring mounts used the option.

Sometimes you have to slew the scope back towards the south before slewing to an object as the program may go ahead and do a shortcut when close to the low and high limits.         Mel Bartels

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SLEWING:     http://www.bbastrodesigns.com/operate_slewing.html

I think of max slew speed in terms of the dynamic range of the motor and drive system. If you adopt 1/3 arcsecond microsteps at 40 microsteps per second with a 200 step per revolution motor, and a max motor rotation of 1000 rpm with a flywheel and minimum torque loading, then your max slew is 12 degrees per second.

Most of us are using 20 microsteps at 1/4 arcsecond size without flywheel with max speed of 2-3 deg/sec.

You can adjust the steps to be coarser or finer or adjust the max slew speed up or down, but you cannot stretch both ends at the same time.   Mel Bartels

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Consecutive slews message appears when the scope is supposed to be tracking using microstepping but has had to slew too many times in a row to try and keep up. The number of consecutive slews allowed before the warning message appears is controlled by MaxConsecutiveSlews in config.dat.           Mel Bartels

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The 'consecutive slews' can be turned off if it is a problem - but it does indicate that something is wrong, namely, that the scope cannot catch up to the encoder coordinates after a certain number of tries (MaxConsecutiveSlews in config.dat).                       Mel Bartels

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4. too small of step size in config.dat            Mel Bartels

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Consecutive slews message appears when the scope is supposed to be tracking using microstepping but has had to slew too many times in a row to try to keep up. The number of consecutive slews allowed before the warning message appears is controlled by MaxConsecutiveSlews in config.dat.

So it means that maximum microstepping speed is not enough, or, that the scope has been incorrectly initialized and consequently the tracking speed asked for is way out of bounds.

Was your scope in altazimuth orientation and pointed right at the zenith? That is what usually causes this.   Ml Bartels

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Yes, if you slew to an equatorial position (an object) and continue tracking, the scope may very well land on a microstep instead of a fullstep. To get it to go to a fullstep, hit the track on/off key twice rapidly. This will turn off the dec motor then in 5 seconds.             Mel Bartels

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Q  I just executed scope.exe and hit 't' key to switch tracking on. Then I used the handpad to center some star through the finder, a few numbers appeared just below the line of AZEC, AAEC, ZZEC and PMC.  What do they mean?

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Q.  Is it possible to use -360 degrees for the az offset? Nothing happens when I do that in a scroll file. I wanted it to help me unwrap the cable that winds up around the az axis from time to time. 

A.  No, break the move into three moves of 120 degrees. The program always looks for the shortest route, hence, a -360 means no move at all.

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Q.  If I set HSTimerFlag to 0, all I get is a high pitched ringing when trying to slew. Halfstepping works fine though. Am I doing something wrong here? 

A.  Slow down the halfstepping if you use HsTimerFlag of 0. The high pitched ring is from way too fast motors.       Mel Bartels

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The MsHsToggleIncrMsPerPWM sets the transition for tracking to occur using halfsteps instead of microsteps. If your microstepping is very tiny, or your Ms speed is too high, and this var is set low, the software may conclude that it cannot track fast enough either micro or halfstep, and will sit there quietly awaiting instructions that it can execute!              Mel Bartels

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Runaway Slews:  Do a reset to either equat or altaz coordinates, then turn on tracking to fix this, then save the config.dat.

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Pressing any key on the handpad will stop a slew.  Mel Bartels

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SCOPE SOFTWARE:        http://www.bbastrodesigns.com/config.html        Program display

Scope.exe version history:  Prior to 2000    Jan 1  2000 - Jan 1 2002   Jan 1, 2002 - present

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Added new config.dat variable, StartInitState. This controls the startup state of the initializations. It operates exactly as the query at program startup: 0 means ask user per traditional menu
options, 

1 means adopt equatorial alignment

2 means adopt altazimuth alignment

3 means adopt no alignment at all

4 means to reuse last alignment. 

Any other option than 0 means that you will not be queried. This is a config.dat replacement for the query menu at startup time. Use it if your answer to the opening query is always the same. Default is 0, to query the user.   Mel Bartels

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Never turn on the stepper power supply when scope.exe is not running.  The state of the parallel port is unknown and it could be set by the computer accidentally to power up the windings.   Mel Bartels

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The return or enter key is the same as answering 'y' to questions posed by scope.exe.Mel Bartels

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(The) Space bar is a kindof page down - there is no provision to page up. If someone wants to try their hand at helping with the software, then that would be terrific.   Mel Bartels10383

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you can make multiple config.dat files and select by using command line scope.exe -c <name_of_config_file>     Mel Bartels

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A quick way to generate the new variables with their default values is to run scope.exe, then immediately quit, saving config.dat on the way out. Then you can go back in and modify the new variables. This will avoid spelling mistakes. If you misspell, the program will adopt a default value, and you may wonder why your new circuit interface isn't working. All the variables in config.dat are case insensitive.            Mel Bartels

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If any variables are duplicated, the last one is the last value adopted. I use this to sometimes have a couple of numbers - by moving them around in config.dat I can hide them or make them active.  Mel Bartels

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A.   You can turn on the safety catch --- are you sure you really want to quit? option in config.dat   ConfirmQuit 1      Mel Bartels 

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The colors are controlled via the opening values in the config.dat file. You can make them blink if you add 128 to them                         Mel Bartels

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A.  Pulse and direction, along with output enable or "motor on/off" will let Mel's program run a number of different commercially available motor and controller combinations. Most of these motor controllers use these three logic level signals to control the motors they drive. For example, I use a commercial controller and stepper motors that were taken off of an industrial machining center to drive a large GEM. Works great! Marty Niemi

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Since real time control is something that you impress upon DOS, I have a control function that decides when tasks are done. These are all tied to the timer tick, which I let run at the default rate of 18.2 times per second.  Everything that the program does - reading your keystrokes, reading the encoders, updating the status on the screen, is tied to the timer tick. Some things are done every timer tick, others are done about once a second.  Sometimes these updates are suspended, for instance, while you respond to a prompt in a window.  Mel Bartels403

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Q.  what compiler can I use to test this (Scope) out with.

A.  I use Borland C++ 4.5. Any compiler from 3 onward will do as long as it has the compile to DOS executable module.  Mel Bartels  11988

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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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the program is growing rapidly (a dozen years ago I tried hard to keep it close to 100k, but it now is 505k). Recently the linker barrier 'dgroup exceeds 64k was reached'. The solution (well, the problem first of all is that there is more than 64k of static data) is to turn on 'automatic far data' in the compiler options. For those compiling their own code, this is how I have the compiler setup:

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OTHER SOFTWARE:

rem SolarSys     then close and save the file.

TEST STRINGS:

The only teststrings allowed:    if( strcmpi( TestString, "NoTest") != 0            && strcmpi( TestString, "PreloadGuidexx.dat") != 0               && strcmpi( TestString, "Track") != 0)   Mel Bartels

TIME:

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Q.  .....set time (makes the scope drive better to the first alignment star) (sends the actual computer time via LX200)  Alexander Urban

To get Guide8 to set the LX-200's date/time, edit the file 'toolbar.dat' and look for the following lines:

# 2373 !focusslo.bmp Focus slow (LX200)
# 2374 !addframe.bmp Add a 'movie frame' .BMP

Add in a line between these two, as follows:

# 2373 !focusslo.bmp Focus slow (LX200)
2422 !17.bmp Set LX-200 time
# 2374 !addframe.bmp Add a 'movie frame' .BMP

...and increase the number of buttons, given at the top of the file.

The next time you run Guide, you'll see a toolbar button reading '17', and when you move the cursor over it, you'll see the hint "Set LX-200 Time". Click on this button, and Guide will send the date/time to the LX-200 (or Autostar or similar Meade-compatible telescope).

Some warnings about this: I've learned that some scopes don't handle the "officially documented" method for setting the time zone; they insist that time zones be integer hours from UTC. I'll be posting a fix for this.   Bill Gray

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If you figure the following: UTC is (plus) or (minus) XX.X hours from your location... you'll have the correct TZ entry.  Ken Hunter

In the case of the Netherlands, the time at Greenwich is:  (Netherlands time) - 1 hour, so you have Tz -1.    Ben Davies

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Q.  I'm also confused on the time zone tag used in config. I've had it set at 6 for the East coast. Is this correct?
A.  East coast should be 5.

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DST is daylight savings time - set to 1 if true, and set to 0 if not Mel Bartels

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Q.  Am I correct in assuming that the DST (daylight saving) variable in config.dat only needs changing if the computer used to run scope.exe    Bernard Heathcote

A.  Scope.exe uses the realtime cmos clock and the dos clock.  I have not experimented to see how daylight savings time affects the OS's calculation of these times.

If in doubt, run scope.exe and see if the local time and sidereal time make sense.             Mel Bartels

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HAOffset - hour angle offset, that is, the difference between what the sidereal time at the zenith is and what it ought to be: this can be caused by an altazimuth mount not being perfectly leveled, or slight errors in your computer time or entered longitude  Mel Bartels

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Sidereal time is the only time that scope.exe uses. It is calculated every bios clock tick (18 times per second), and as I just said, the only time that is referenced in the program.

What you can do is to watch the sidereal time and local time displays, to be sure that the laptop/computer is not running fast or slow. This should not be an issue - last computers I saw run badly out of time were some of the 386 machines.

... turn off tracking then you can slew in equatorial offset one hour in RA. Wait one sidereal hour, and instruct the program to slew back to the object. If time drift is a problem, it will show in the display and object centering.

Again, any type of polar misalignment also masquerades as fast or slow tracking depending on where in the sky you are pointing. Mel Bartels6206

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Sidereal time calculated in scope.exe based on:  longitude in degrees (measured west from Greenwich), timezone, daylight savings time, local computer time and date.

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When doing the initializations using the handpad, the sidereal time is calculated for you - you have no opportunity to enter the time as this is supposed to be real time. The sidereal time calculation is based on the longitude and time zone as entered in config.dat. It is really the time difference between inits and coordinate conversion when slewing to an object that counts. That's why you don't have to enter correct longitudes and time zones - the relative time between the inits will be correct, and when you do a 'reset to equat' the program handles the time error for you. If you do enter correct longitude and time zone values in config.dat, then you do not have to do a 'reset to equat' when you startup scope.exe again.   Mel Bartels

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Q.  In what time must the PC clock be set up? (Local or UT)?  

A.  Your local time  Mel Bartels
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Does the accuracy of the PCs clock effect scopes accuracy?

If your laptop/computer clock drifts, then so does scope.exe, as it relies directly on the clock. All other telescope control software does too! Mel Bartels

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The lat/long/timezone are used for the sidereal time calculation. If you are using an equatorial mount, then sidereal time is important as it determines the hour angle of the object to be observed (HA = SidT - RA).

Otherwise it has no bearing on the initialization process. That's why for altazimuth mounts you can go into the init display menu option (hotkey 'i') to see if the calculated latitude matches your geographic latitude. Allowing for unlevelness of your mount, they should agree.                   Mel Bartels

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Q.   We changed to daylight saving time since I last had the scope outside.
A.  It might cause early or late GEM flips, but will not cause tracking and goto to be really off.  Mel Bartels

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if you find the scope tracking too slow, check your sidereal time vs local time after running the program for an hour. I found a Win9x machine where the bios clock ticks are being dropped every so often, causing the sidereal time to run a few seconds slow after an hour of tracking.  Mel Bartels 

TORQUE:

Most situations can be happy with 10in-oz torque and 1a at supply voltage.     Mel Bartels

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To increase torque while microsteppping, lower the microstep parameter MsPause to 0 in config.dat.  To increase speed for slewing, lower the MinDelay value in config.dat.    Mel Bartels

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#1 Rotational speed vs. Torque while Micro-Stepping:   The PWM values MsDelay and Mspause will affect this, but only during  micro-stepping.   MsDelay controls the over all frequency of the PWM, Higher frequency = Higher coil resistance, and lower torque MsPause controls the duty cycle, which directly affect torque while Microstepping. Decreasing MsPause will increase torque.

#2 Rotational speed vs. Torque while Half-Stepping:   The HS values MinDelay and MaxDelay will affect the Speed, which will result in 'X' torque

After the above software options comes the Hardware categories,

#1 Add a Flywheel to the stepper shaft:   The flywheel acts as a buffer to ensure the motor keeps spinning between steps and avoids stalling, much like a flywheel on an automotive engine.  Since you can't get something for nothing, you do trade Acceleration for an increase in motor speed and/or torque.

#2 Increase input voltage to increase current flow, which increases torque.

Mel's software allows for an option to engage a Higher Voltage during Halfstep slews, which can solve for many problems   James Lerch

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Unless you are using more than 12 volts or flywheels, getting the MinDelay down to 350 is about normal, if not better than average, from what I have seen. The faster the steppers spin, the less torque they have. Ls

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 I have exactly the same conclusion: I use scope with two laptop, one with 486 DX 25 the other with 486 SX 25. The torque is lower on the second (with the same settings). It seems better to use computer with math co-processor.          Jean Claude Amacher

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Should be no difference between altaz and equat operation - the motors do not know the difference.  My first guess is that the equat mount needs more torque, so decrease MsPause in the config.dat file. Mel Bartels

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Tune out the torque from the steppers to the bare minimum for good overall operation. This is done in the Msparms section while running your scope.                         Leonard Stage

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1) Make sure you have a flywheel on each motor.

2) put a current meter in series with the common lead to one of the steppers..what is the current? Measure it at start of the slew. The current should start out high, then ramp down as the motor speed increases. If you're having trouble with torque, you want to increase the current. When slewing, you must decrease the motor RPMs via the half step parameters in Mel's program, or increase the supply voltage to increase torque. As a starting point, try adjusting the HSparams to get the current close to the max rating on the motor. The slower the motor turns the greater the current. For example, my motors are rated at 5Volts and 1 Amp = 5watts. I operate my motors from a 15 volt supply. When I start a slew, the current is about 0.6amps. At max slew speed, the current is 0.3amps. 15Vx0.3A=5watts. Notice, I'm running my motors at their rated power, but over their rated voltage. Using the higher voltage allows the motors to run faster while keeping the current/power (this torque) near max. 

3) Now measure the current during tracking. Adjust MSdelay and MSpause to lower the tracking current to the minimum your motors can take while providing adequate torque. If possible, you'd like to get the power down to les than the rating (~1/2 rated power).   

4) Stepper motors also have a tendency to become unstable if they are stepped very fast without a load on the shaft. In such a case, the stall is not due to inadequate current or torque. My motors can be made to run extremely fast if I simply put my finger on the flywheel to add drag while running them with a large overvoltage. Try holding firmly on your motor shafts while slewing. If you can easily stall them with your finger, then you need more current and should consider increasing the voltage. If they run better with the resistance from your fingers and you can't stall them, then you might be ahead to lower you voltage a little.      Larry Bell 9498

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The slower you move the steppers the more torque they will have when half stepping. ...referring to tracking torque, the motors/msparms, mspause and msdelay will give you the adjustments for that. Lower number values for each will increase torque typically.  

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TRACKING:

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Set speed of tracking by adjusting the fullstep size in config.dat, specifically AltFullStepSizeArcsec AzFullStepSizeArcsec You gotta figure this from gear ratios or from observation Mel Bartels 

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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  

My program "SolarSys" ....computes the position and of the Sun, Moon and the planets plus their drift rates.  Run the program before running "Scope" and it creates two datafiles.  One for position only and the other with drift rates.  Use the Comet dat file command to load the datafile with the drift rates.  The program is in the file section of this group.   Rex Kindell

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MsHsToggleIncrMsPerPWM  At some point before reaching this speed, the program will switch from PWMs to halfstepping, this speed being MsHsToggleIncrMsPerPWM.  MsHsToggleIncrMsPerPWM should be less than or at most, equal to MaxIncrMsPerPWM Mel Bartels

Assume PWMRepsTick = 50, MaxIncrMsPerPWM = 8, MsHsToggleIncrMsPerPWM = 4, Ms = 32, and microstep size = 0.2 arcsec

When the scope is tracking the scope will switch to halfstepping using timing based on the PWM rate when it hits MsHsToggleIncrMsPerPWM. This will occur when the number of microsteps required to be moved per PWM exceeds 4 which equates to a tracking speed of 18.2 * 50 * 4 * 0.2 = 728 arcsec/sec. The drive will then continue in tracking mode using halfsteps timed by the PWM rate until it gets to the next limit set by MaxIncrMsPerPWM at which time it will exit tracking mode and go into slew mode. The tracking speed at which this will occur in the example given will be 18.2 * 50 * 8 * 0.2 = 1456 arcsec/sec. Mel Bartels

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MsHsToggleIncrMsPerPWM says how many microsteps can be skipped over before the program goes into halfstep tracking mode.  Halfstep tracking mode is a sort of last ditch effort by the program to attempt tracking when the microstepping speed is otherwise way too slow.  Sometimes it works and sometimes it doesn't.   Mel Bartels 13843

MsHsToggleIncrMsPerPWM says how many microsteps can be skipped over before the program goes into halfstep tracking mode.  Halfstep tracking mode is a sort of last ditch effort by the program to attempt tracking when the microstepping speed is otherwise way too slow.  Sometimes it works and sometimes it doesn't.  Mel Bartels  13843
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there is a different timing method used depending on whether the drive was slewing or tracking.    Lets assume PWMRepsTick = 50,  MaxIncrMsPerPWM = 8,    MsHsToggleIncrMsPerPWM = 4,    Ms = 32,    and microstep size = 0.2 arcsec    

When the scope is tracking the scope will switch to halfstepping  using timing based on the PWM rate when it hits MsHsToggleIncrMsPerPWM. This will occur when the number of microsteps required to be moved per PWM exceeds 4 which equates to a tracking speed of 18.2 * 50 * 4 * 0.2 = 728 arcsec/sec. The drive will then continue in tracking mode using halfsteps timed by the PWM rate until it gets to the next limit set by MaxIncrMsPerPWM at which time it will exit tracking mode and go into slew mode. The tracking speed at which this will occur in the example given will be 18.2 * 50 * 8 * 0.2 = 1456 arcsec/sec.            Andy Martyn   5918 

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it is possible to bring the dec motor to rest on a fullstep. You can do this now by hitting the 't' for track on/off twice rapidly. This forces the dec motor to the nearest fullstep to end tracking, then resumes RA motor tracking immediately. Mel Bartels

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put the handpad into one of the guide modes if you wish tracking to continue while using the handpad. Otherwise the handpad moves the scope in one direction at a time. Mel Bartels

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Q.  I can´t understand that you say as "a bigger hole at the zenith that is not trackable "

When an object approaches the zenith, the azimuth is basically fixed, and the altitude creeps up to 90. When it crosses zenith, the azimuth must change 180 degrees very quickly, so the altitude can start creeping down from 90 to 0. If the object is too close to zenith, the scope can't slew the azimuth around fast enough.     Mike Lindner

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1. At the lowest speeds...the software moves in 1 microstep increments (no matter if it's 10, 20, 40, or 6 microsteps per full step.)

2. At slightly higher speeds, the software will skip microsteps...it'll move from microstep 0 to 2, to 4, etc. (or 0 to 3, to 6, etc.) to maintain the required motor shaft speed. (This is still microstepping.)

3. At higher speeds halfstepping can be incorporated in the PWM microstepping routine. The point at which this transition happens is defined by MsHsToggleIncrMsPerPWM.

4. The highest microstep tracking speed attainable is defined by MaxIncrMsPerPWM, which is effectively microsteps/2...which results in halfstepping at the PWM rate.

5. Above the speed of MaxIncrMsPerPWM halfstep slewing is used.

In the above discussion, the number of microsteps does not determine how fast you can track...that limit is set by MaxIncrMsPerPWM, which can never be higher than microsteps/2. (Ok, if you are running at 40 microsteps per full step, and set MaxIncrMsPerPWM = 3...it'll be a far slower speed than if you are running at 6 microsteps per full step, and set MaxIncrMsPerPWM = 3...but then you can set MaxIncrMsPerPWM = 20 and have the same max speed.)

Based on config.dat entries...there is no extra torque available for configurations with smaller numbers of microsteps. Software skipping of microsteps makes 40 microsteps per full step behave like 6.  Tom Krajci

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I too feel that it is easier to get smoother tracking from older laptops than newer ones.  2/26/2000  Mel Bartels

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Q.  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

A.  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

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Q  Any hints to get 50%-50%-pulse at track-mode?

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VIBRATION:      see noise    

WEATHER: 

I developed a beta version of SKY TRANPARENCY forecast. This new forecast is based on moisture in the airmass. I do integration of the moisture throughout the air column for each gridpoint of the regional model and give more weights for the boundery layer (surface-1000 metre) and at the jetstream levels. I did many adjustment to the variables to fit my own and a friend observations of the sky transparency and water vapor satellite pictures. It seems to work quite well and this will be helpful for observers looking the the darkest sky or planning to drive long distances to have access to dark skies.  

Hoping these new images will be usefull to the community.... I invite you to publish the site to all your club members and include a link in your local web page. http://www.cmc.ec.gc.ca/cmc/htmls/mainpage.html   Allan Rahill         

YAHOO:

...Yahoo has just made a sneaky change to everybody's 'Marketing Preferences', the result of which will be a load of spam. So, I've just been in and changed back what they've done so that I won't be receiving their ads! They had changed ALL of my *No's* to *Yes!*

Here's what you need to do: Go to My Groups and click on Account Info, verify your password if it asks you to, and your Yahoo ID card comes up. Click on 'Edit your Marketing Preferences' and change all those Yes's back to No's! Click Save Changes.  Paul Greenhalgh

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Z1 Z2 Z3     see also analysis files

A.  I'd do the Z3 with the analysis file at some point to determine the Z1 and Z2 numbers. Once you get Z1 and Z2, via an accurate Z3, then you can adopt those Z1 Z2 numbers, and do a simple 'a' altitude offset. If Z1 and Z2 are fairly accurately well characterized, then the 'a' altitude offset will work quite well.  Mel Bartels

Websites of Scope-Drive members:

Albert van Duin     Andrew Wall    Antonio Pena     Ben Davies   Berthold Hamburger     Bob Norgard   Brad Davey     Chris Everaert  Chuck Shaw     Dan Gray       Frederic Gea     Francois Tisserant     Greg Granville   Jack Shell       James Lerch        Jan Boyle       Jan van Gastel     Jay Leblanc     Jean-Charles Vachon     Joe Garlitz      Johan Coussens      John Pike      Jurgen Liesman      Lenord Stage      Marc Durey      Mark Rice    Marty Niemi     Martin Cibulski   Mel Bartels      Michael Linder     Nils Olof Carlin   Paul      Paul Shankland       Rafael Gonzalez     Raoul Alverez    Rex Kindell  Richard Bowden      Roberto Pepitone      Rolf Apitzsch     Ron Depack       Sloboyko      Steve Goldman            Steve Mitchell      Soren Madsen  Stan Kohut       SteveB  Tracy Wilson     Thomas Janstrom      Thom Iwancio      Tom Krajci     Tracy Wilson      Vincent Steinmez      Wilfried Wacker     William Carroll       Yvonne and Alexander Urban