MDM Trouble Report for 2004 Nov 12

Telescope: 2.4m
Observer(s): Thorstensen, Sheets (Dartmouth)
Instrument: echelle direct + 2 in FW

Problem(s) Encountered:
Two problems:

1) The dome auto-enable switch on the black DFM control panel
is not positive -- at the start it was only making intermittent
contact and we lost a few flatfields because the telescope was
not looking squarely out of the dome. We were able to establish
contact by wiggling the switch, but this could be serious if an
observer didn't diagnose it properly -- the switch can be in the
up position but not making contact.

2) After we restarted late at night, he drive slipped frequently 
at positions in the east (I didn't try the west).  The symptoms
were a slip-jump motion with about a 2-second cycle time, 
starting as a low-amplitude wiggle and progressing to a near
complete sticking of the HA motion.  When it gets bad, 
attempting to  catch up  with the hand-paddle  set  motion 
doesn't help, and approximately doubles the frequency of the 
slip-jump cycle.  As has been remarked many times in the past,
the problem appears to be temperature-dependent -- it's much
colder tonight than it was last night.  The problem recurred
maybe every 8-10 minutes.  The drives did not make any obvious
noise during slipping episodes.  While the HA encoder can be 
used to see the problem during daytime, seeing the fine 
structure of it (little wiggles etc.) would require being
on sky, I think, since then one can see small star motions
in real time.

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

Submitted on 2004 Nov 13 [5:58:01]