MDM Trouble Report for 2008 Oct 25

Telescope: 2.4m
Observer(s): Prieto (OSU)
Instrument: Modspec & Retrocam

Problem(s) Encountered:
Very strange problem occurred, stopped observing early.

I had finished observing an object at RA=19:54 DEC=+20:53 
(HA=+02:06) and sent the coordinates to move to an object 
at RA=22:27 DEC=+00:57. The telescope moved past the object 
very far east, and at some point the hour angle reading in 
the TCS stopped working (almost froze, changing very slowly) 
although the telescope was still slewing east. I had to stop 
the movement by hand from the xtcs. At that point it already 
had lost it's pointing completely. 

I slewed by hand back to zenith and set the ra/dec encoders there
(Paul was here helping look at the telescope). I tried moving 
to a bright star that was east of zenith. The reading of hour 
angle would move very slowly in the TCS, but the telescope was 
actually slewing east and had to stop it from the xtcs before 
something bad would happen. I moved the telescope back to 
zenith by hand again and reset the ra/dec encoders.  

After that restarted the TCS computer, but it didn't help. 
Note that it's *only* moving east. If I use the hand-paddle
and move W/N/S the reading in the TCS is alright, but if 
I move east the hour angle doesn't change (in fact it does
very slowly after you start to slew).  
    
     

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Submitted on 2008 Oct 26 [1:34:51]