MDM Trouble Report for 2002 Mar 12

Telescope: 2.4m
Observer(s): Noel-Storr (Columbia)
Instrument: CCDS

Problem(s) Encountered:
The telescope was pointed at an HA of about 0 - +15 mins; 
declination +2 degrees at around 8pm local time when it began
to 'skip' in very fast movements of about 4  to the East. 
[The skips were substantiailly faster than stars trail across 
when the tracking is switched off, and appeared to be 
 instantaneous  in nature.]

This happened in 'single skip' events, about 5 times. 
On two occasions the skip repeated several times in 
individual 4  ish steps.

The encoders tracked the motion and a 'send' and 'go' 
brought the telescope back to the original position.

This sounds like a similar problem to that reported by
Marianne Vestergaard last week. Though she told me that
this was a 'temperature problem'. At the time this occured the
outside air temp was 13C and the truss arms were at 13.4C.
Both were slowly cooling (about 1C/hour), and the problem did 
not repeat at any other point during the night. (The next 
target, which I moved to immediately after the spate of 
troubles, was very close to HA ~ 0 but with Dec +48d 36' and
was trouble free).

Though this did not cause any problems, it would be useful
if this was somehow characterized / explained as if it
occured in the middle of a long exposure it would be 
problematic. The shift was much faster than the guider PC 
could correct for.

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Submitted on 2002 Mar 13 [7:10:00]