Lost (and found) pointing

Thursday, March 31, 2022 5:54 AM

Problem(s) Encountered:

We lost the pointing at the beginning of the night observation. The telescope position ('MDM1.3m Control panel') is not same as the target's position. I tested another target, and it still has RA_OFFSET~1m18s, DEC_OFFSET~7'0''. Then I point the telescope to the zenith, without tracking and enter: zero ra=(LST) dec=31:57:12 equinox=2022  It still doesn't work. Finally, I found the value for tilt sensor motion cannot change when I move the hand paddle. It is always at [-491,+458] at zenith. Next, I tried the offset (in the telescope control panel). The value for motion still didn't change. We close the dome at 12:00 am LST.


Firstly, thank you to Jules for getting the telescope back to zenith during the night.  Somehow the pointing was way off.  Note that the tilt sensors really only change when using the hand paddle when the telescope is near zenith.  Once the telescope is more than a couple degrees away from zenith, the tilt sensors become useless at helping verify telescope position.  If this happens, it is recommended that the dome lights be illuminated so that the observer can get the telescope roughly to zenith by eye.  Then positioning can be touched up using the tilt sensors and hand paddle and encoders can be zeroed to zenith values.  After that, it is recommended to center on a bright star and once again zero coordinates to those of the star.