Paweł replied to the topic 'indi_celestron_aux' in the forum. 10 months ago

The initial driver was intended only for the AltAz mount, like the Evolution. The Eq mode is an afterthought. Nevertheless, the same approach will still work for Eq, since no mount is perfectly aligned and the input from the alignment routines can be still used to correct rates in Dec and RA - thus eliminating the necessity for very precise polar alignment. Thus, I would not switch to a completely different tracking mode for Eq mounts. Since the standard Eq mode (sidereal rate in RA + guiding pulses) is much simpler, it should be fairly easy to add it as a switchable option. Remember that not everyone has a guider - thus removing corrective guiding would make the driver less functional. As for the fight between the tracking and guiding pulses: I do not know really. But, I think that it should be fine since we are controlling the speed not the position and the target position is not changing. Thus, we are correcting only the errors of the mount not the tracking rates and target position.The motor controllers handle constant angular velocity and two types of goto movements. You specify angles for the gotos, and then you specify the tracking rates in both axis (with MC_SET... commands). These rates are constant - if you switch off the driver or lose the connection, the scope will keep rotating with constant angular velocity. That is why it may be unsafe to operate without limit switches or supervision. The 30s period is arbitrary and probably fine for visual observing. It is definitely not enough for high-Alt positions (the AZ rate changes rapidly). We are actually sending adjustments every second in the current driver based on +/- one-minute position difference. The controllers seem to have no problem with this rate of adjustments. In my view the guiding does not shift the position on the sky it only corrects for the errors in the mount. The tracked position (thus also tracking rates)  does not change. So in this respect we should be fine as long as we are not reading back the encoder positions to modify the rates. The first version of the driver actually did just that, and I had huge difficulties with making it consistent. At present, the tracked position is changed only when we use movement controls. But in this case we are supposed to move the tracked position on the sky (that is an assumption). 

Do not hesitate to ask if something is still unclear. The interplay between tracking, guiding and manual movement is really tricky to get right. I do not think we can avoid making some assumptions. Otherwise, there are simply too many degrees of freedom.
 

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