MDM Trouble Report for 2001 May 31

Telescope: 1.3m
Observer(s): Jules Halpern (Columbia U.)
Instrument: Echelle CCD Direct

Problem(s) Encountered:
The good news is that I discovered the cause of the sticking
filter wheel.  But there is some bad news as well. . . 

The filter wheel got stuck again when I was observing far in
the east (PG 1633+099, secz=1.74).  When I couldn't get it to
re-initialize, I went to zenith, and a fairly loud, continuous
noise began to emanate from the filter wheel.  After resetting
the MIS, the noise stopped.  Since I have some experience in
removing this filter wheel, I decided to open it up.  As I was
removing the filter wheel, I noticed that the manilla card that
was used to cover the central hole in the wheel had come loose,
and was wrinkled up and lodged against the U filter.  The net 
result is that the U filter is badly scratched, and may have to
be recoated, or possibly just retired. (The remaining filters
appear to be undamaged.)  I removed a few pieces of black tape
that had become distributed on the wheel and inside the housing.
After verifying that there appeared to be no more loose pieces
of tape, I reinstalled the wheel (without the central card), and
I am now observing again.  During the day, I recommend that the
the wheel be removed and the filters and interior of the housing
be examined again. I would like to discuss whether or not we 
really need that central baffle, too.

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Submitted on 2001 May 31 [22:05:53]