Pointing issues, dropleaf errors, etc...

Monday, September 27, 2021 11:01 AM

Problem(s) Encountered:

Got error 'error dropleaf slit busy' upon trying to re-open. I did telescope stop/start (although telescope status indicated everything was running) which fixed that. Completely lost point-
ing on re-opening, couldn't figure out how to offset the telescope to effect the left side tilt meter. Closed without solving this problem. On trying to close again, I ran 'tx dropleaf close' and got a  log message of 'done dropleaf cantopen=rain'. I restarted tcs following the troubleshooting and that worked. 


Unfortunately, the tilt sensors only really give you pointing information very close to zenith.  This morning, I found the telescope more than 2 hours over to the west and almost 8 degrees north of zenith.  If one finds themselves this lost, the best bet is to take a deep breath, turn on the dome lights (through the web-based power switch on workspace 4) and work the telescope back towards zenith.  In this case, it would have been apparent that the telescope was well west of zenith.  This can be verified by the fact that the tilt sensor’s first value was positive.  Since the TCS GUI erroneously indicated that the telescope was at zenith, one would have to issue a command to move the telescope in the proper direction (in this case, east) by demanding an HA value greater than 0.  The same would go for declination.  In this case, one could verify that declination was above 32 degrees because the second tilt sensor value was positive.  Therefore, one would have to issue a command demanding a declination less than 32.  This would not correct the positioning readout, but would get the telescope closer to zenith, ultimately allowing the user to utilize the tilt sensors to dial in pointing.  So for this case, the user would enter the following:
tx point ha=-2:18:39 dec=25:16:06
Since I have the benefit of writing this after correcting the pointing, I knew the exact values needed.  In the moment however, you would have to iterate until you got tilt sensor values closer to zero (preferably within ±050 of zero).  After this, the virtual hand paddle could be used to move the telescope by steps of 60” at a time until the nominal tilt sensor values was reached.  Then, and only then, could the telescope coordinates be zeroed out as follows (with tracking OFF):
zero ra=LST dec=31:57:12 equinox=x
where LST is the local sidereal time at the moment the ENTER key is hit, and x is the current equinox, as noted on the TCS GUI.