MDM Trouble Report for 2001 Nov 26

Telescope: 2.4m
Observer(s): Chris Gerardy (Dartmouth)
Instrument: TIFKAM

Problem(s) Encountered:
There appears to be a problem with the prefilter wheel
on TIFKAM.  When changing settings, it appears that the prefilter
wheel sometimes gets stuck, or otherwise fails to reach it's 
destination.  I first noticed the problem when attempting to 
put the IJH grism in, (prefilter position 8).  Prospero came back
with the following error:

Setting Prefilt...
Error: Command returned error
ERROR: step-out encountered
Error Setting the PreFilter Wheel
Programming Error: invalid error code:	-99
PREFILTER request aborted with errors.
Execution error in Prospero command.
Command: prefilter 8

Following this error, I tried sending the prefilter wheel to the
other slots, and prospero gave no errors.  Then I sent the 
prefilter wheel back to position 8, and it appeared to work 
correctly.  

However, it also appears that the prefilter wheel isn't always
reaching its destination, even when prospero doesn't give an 
error.  Sometimes, when setting the prefilter wheel to the  JHK 
grism, (setting 4), everything appears to work correctly as 
far as prospero is concerned, but the grism is clearly not in
the correct position as there is no dispersion of the beam.  
Sending the prefilter wheel to another position and then moving
it back seems to usually solve this problem.  

-Chris



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Submitted on 2001 Nov 26 [14:53:31]