High Declination Pointing Issues
Saturday, October 12, 2019 8:57 AM
I was unable to point the telescope to a target near the meridian at Dec=+79. I saw this at positions both east and west and was never near the pointing limit. The JSkyCalc GUI gave a slew error and didn't move the telescope. I had definitely observed objects at similar declinations (including the same target) with this telescope in the past, so I did some experiments. I restarted TCS, homed the Dec drive, and checked the Dec controller, but none of those things worked. As an example: after turning off tracking, the command point ha=-02:00:00 dec=+73:00:00 would work point ha=-02:00:00 dec=+74:00:00 would not work with an ERROR point illegal Dec 90 (trying it with dec=+75 would give a similar error, but would say Dec 91 instead). I tried creating some fake targets in my target list at various locations in the north and also used the point command, but both failed above dec 74.
We left this unresolved and moved on to other targets.
Tried moving north of dec=72 and failed with errors like illegal dec 91 and illegal dec 93. Brought everything down, cycled McGraw and reset the TCS electronics. After this, the telescope would go to demanded positions >+72 again. Not sure what the deal was.