MDM Trouble Report for 2002 Oct 29

Telescope: 2.4m
Observer(s): Thorstensen (Dartmouth.)
Instrument: modspec + echelle

Problem(s) Encountered:
The singing telescope is back, and the RA tracking is inter-
mittently slipping badly.  There were about 6 episodes of
slipping during the night, typically lasting a few minutes.
Most of it happened in the southeast but it also slipped once
at +60.  

The slipping is preceded by the singing noise for a minute or
more.  The singing noise is usually rhythmic; I timed 10 pulses
in 17 seconds.  When the slips occur the telescope jumps about
3 seconds of time toward the east.  Sometimes it does this
several times in a row, and sometimes it even gets  stuck --
it tracks for a few sec, then jumps, then tracks, and doesn't
move.  I went out and looked at the RA drive during one of the
jumping episodes; I could see that the whole mechanism was
seizing up, including the 8-inch toothed wheel, the worm
gear which drives it, and the little pulleys with the rubber
belts.  The TCS position displays correctly track the 
jumping telescope's position.

By the way, the control room is *much* more pleasant with the
guider PC gone - thanks again for moving it.  At some point 
it would be good to figure out a way to repeat the PC's beep
in the observing room but that's not urgent.

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Submitted on 2002 Oct 29 [6:44:42]