MDM Trouble Report for 2006 May 25

Telescope: 2.4m
Observer(s): Nick Morgan (OSU)
Instrument: 8k mosaic

Problem(s) Encountered:
I had three cases of the TCS reporting 'RA and Dec encoders not
responding'.  I believe I know what caused the first two, 
but I don't know what caused the final one.  

The first happened after I got an 'outside soft limits' message
on the tcs.  The telescope tracking stopped by itself (because 
of being close to the limit, I assume), so I sent the telescope
to move to a new target closer to zenith.  After clicking 
'go' on the xtcs, the tcs reported 'RA encoder not responding'.  
The telescope was moving, however, and the airmass started to 
increase from 2.0 to 2.2. I thought something was wrong that
it was moving closer to the horizon so I hit stop on the xtcs.
(Was it moving along dec but not ra?). The 'RA encoder not 
responding' message stayed on the tcs for several minutes 
before eventually dissapearing by itself.  Once gone, 
I was able to move the scope to zenith using the dome 
paddle and reestablish pointing.

The second instance occured when the telescope was slewing to a
target and I think I may have started using the control-room
paddle to search for an 8k guide star during the tail end of
the main slew.  Again, I waited several minutes for the
encoder not responding message to go away and then was 
able to repoint at zenith.

The third instance occured as the telescope was slewing into
position for morning sky flats.  I went from 2 hours east to 2
hours west.  When the move was nearly finished, the tcs said
'DEC encoder not responding' and the telescope started 
oscillating in RA by about 10 seconds of time every 5 seconds 
or so.  I did not touch the paddle or issue any other tcs 
commands during the slew, so I don't know what might have
caused this.  It did ~5 oscillations as I watched the stars 
swing back and forth on the guider tv before I hit 'stop' on 
the xtcs and took my skyflats.  Again, the message dissappeared
after a minute or so and I had no trouble parking the telescope
at zenith.

------------------------------

Submitted on 2006 May 26 [7:10:12]