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LX200 GPS train drives.

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#1 BKMaynard

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Posted 19 September 2023 - 08:11 AM

Does training the RA drive affect the tracking performance?


Edited by BKMaynard, 19 September 2023 - 08:16 AM.


#2 carolinaskies

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Posted 19 September 2023 - 09:09 AM

Training the drives affects pointing accuracy.  The effect of training the drives tells the system how far the gearing is moving the telescope.  If you don't train the drives it's akin to not knowing how long an inch actually is, but when trained the drive knows how many pulses equates to arc seconds of motion. Typically you point the telescope to a stationary object like the top of a phone pole then initiate training.  The telescope moves then you recenter again and it compares the result and knows the motion. 

If you have not properly trained the drive in RA then it may have the wrong information so when it thinks it's moving at sidereal rate it might be slightly slower or faster over some period of time.  However, other issues can cause tracking error including weak power into the telescope.  



#3 bdoyle

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Posted 19 September 2023 - 12:38 PM

I always thought the drive training was a form of backlash comp. Fixing on a point and then approaching it from both sides would allow the controller to see "dead" motion. Pulses or encoder counts to degrees of motion should be a fixed amount.



#4 carolinaskies

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Posted 19 September 2023 - 02:25 PM

I always thought the drive training was a form of backlash comp. Fixing on a point and then approaching it from both sides would allow the controller to see "dead" motion. Pulses or encoder counts to degrees of motion should be a fixed amount.

There's a backlash compensation adjustment in the utilities for hand control response to pushing the directional buttons.  For train drives the axis direction differential likely is measured during the training session so the axis will move the correct starting pulse corresponding to which way it is being driven.  Thus backlash is compensated for in the initial movement if it's in the reverse direction. Once the motor is driving at normal rate pulse length doesn't have to be modulated any differently.   On standard mounts there are no absolute encoders so the pulse length under motion after initially measured is what training drives is measuring and storing.  
 




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