MDM Trouble Report for 2009 Mar 27

Telescope: 2.4m
Observer(s): Kathryn Stanonik (Columbia)
Instrument: Echelle

Problem(s) Encountered:
The first hours of observing went fine, but at 9 the wind picked 
up slightly (20mph) and the telescope began slipping to the east 
in RA.  The wind would push the target slightly off center, which
the guider started correcting for, but then it would make a 
sudden jump of about 2 seconds east in RA.  This was reflected in
the TCS telescope coordinates.  The telescope was not pointing 
directly into the wind.  I also started hearing a squeaking 
coming from the telescope with each jump in RA.  The telescope 
would point stabilly for as long as 30 minutes, but would 
ultimately jump once or several times sequentially, even after 
I stopped guiding.  I tried pointing the telescope to zenith 
and back to my target, but the problem persisted.

As I was trying to get 15 minute integrations, these jogs in 
position were particularly troublesome.  At about 9:30 I 
called Bob to see if he had any advice.  We located the 
squeaking sound as coming from the RA drive on the back of the 
telescope, where I could see the belt slipping backwards 
occasionally.  We also found that in the computer room the RA 
stepper motor drive needle was jumping far to the right 
past 1.  Bob seemed to know what this meant...

At this point, it was too late for Bob to come out, so I stowed
the telescope at zenith for a half an hour, and turned off the 
drives and tracking, and then tried observing again.  I broke 
my long exposures up into 2 or 3 minute chunks, and selected 
targets away from the wind.  The telescope then pointed 
steadily for  2.5 hours, at which point it started slipping 
again.  I again stowed the telescope for 15 minutes, and again 
had 2.5 hours of successful observing.  I did this one more 
time before dawn.  The telescope exhibited no slipping for the 
first hour after stowing and turning off drives & tracking.

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Submitted on 2009 Mar 28 [5:50:45]