Quote:
Originally Posted by JA
Hi Michael,
I would suggest you go back to ZERO or as close as possible, to understand the root cause of the problem. That means testing ONLY the mount, with nothing mounted or connected, just the hand controller to start the tracking. Then if something is discovered with mount tracking that indicates a glitch in tracking , it's the mount at fault. If nothing is found add further complexity/variables and then look for a glitch, reassess and continue until potential cause is found.
We know from tests (imaging with and without guiding) that you've done that the issue presents itself every few minutes with a similar magnitude of ~12.5 arcseconds on both RA and DEC drives.
As I discussed a few posts ago, given the Skywatcher stated 705:1 drive ratio of the HEQ5 mount, the 12.5 arcsecond correction pulse you are experiencing should equate to just under one second of elapsed time or 3 degrees of rotation FORWARD or BACKWARD of the RA or DEC motor pulley (or motor pinion gear in the case of a standard non-belt modified HEQ5)
Watching an ~10mm diameter pulley rotate and observing whether it stops , retreats or advances 3 degrees in one second may not be that easy to do. (understatement) and that's why your earlier idea to video the drive pulleys was 100% on the money, BUT you did it in time lapse mode where one rotation of the motor pulley took about 12 seconds instead of ~120 seconds. You should go back to that investigation and video the drive pulley, zoomed in as close as possible to the pulley, in real time not at ~10:1 timelapse. Then when you have several minutes (say 10 minutes of realtime video, open the video in a video editor and go through it frame by frame looking for any odd movement or lack of movement, be it: stopping, reversing direction, slowing speeding etc... Yes it will be a few thousand frames but at a typical video frame rate of 30 frames/second you should see everything you need to see to confirm the existence of a possibly 1 second or so long event that occurs every few minutes. If you don't see anything go longer until you're certain of an issue or that there's no issue.
As an alternative, to amplify the tiny motion we are trying to observe, you could try also mounting/balancing a tiny red laser pointer to the top of the motor drive pulley with some blue tack, place the HEQ5 in a large dark room so that it is lying on its side flat on a table and look for non-smooth/start/stop etc.. motion of the red laser dot across the walls over several minutes.
Best
JA
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Ha yeah your right I made the video 10x more inaccurate by using time lapse. a major issue I had with trying to time it was judging when exactly a full turn had occurred. I will try it again soon though and see what happens, and specifically with and without a guide camera connected and running taking images (as I still suspect it might be the connection of these items causing comms errors, after the result with the guide cam monitoring from a device not connected to the mount which showed no spikes)
I also want to pursue the test I did with the guidecam on the computer while asiair drove the mount, see what happens when imaging/not imaging.
Be interesting to see if I can clear run of non streaked images (within the range of pec errors anyway) or does taking Images on the asiair cause spikes I see on the computer monitoring the ra/dec errors. Bonus points if I can go back and forth between these errors while filming the cogs turning with time stamps so I can match up frames to phd2 spikes.