MDM Trouble Report for 2010 Feb 8

Telescope: 1.3m
Observer(s): Fesen (Dartmouth)
Instrument: Direct Echelle

Problem(s) Encountered:
The telescope in either guide or unguiding mode will 
instantly jump around up to 2.5 arcseconds in a north/south
motion and then just as quickly return to its nominal position.
And then sit there for a few seconds before jumping again.
The problem is worse at large hour angles but occurred sometimes
at small hour angles.
As an experiment...since I couldn't take decent images with this
problem (all the stars have n-s lines through them)...I
put the telescope in stow position to see if it was a balance
issue. In unguided mode it held the star in the guide box
nearly perfectly for 10 minutes with no N/S jumps.
At +1.5 hr over at 49 degrees, the telescope also behaved
perfectly. It was rather cold (T= -2 C) but am not sure temp
has anything to due to it since it didn't happen in stow
position.
This is a less severe version of the  nodding  problem in that
the telescope jumps only 1 or two arcseconds up and down instead
of 10 - 20 arcseconds.

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Submitted on 2010 Feb 8 [5:55:38]