MDM Trouble Report for 2012 Sep 21

Telescope: 1.3m
Observer(s): Sebastien Lepine (AMNH)
Instrument: Direct + 4K

Problem(s) Encountered:
Noticed a slow but significant drift of the stars 
on the ccd image over the night. The same field was
observed from 7pm to 1am, with flawless guiding. However,
all stars were seen drifting, by about 20 pixels along Y axis 
and by over 60 pixels along X axis, between the first (7pm) and
last (1am) frames. There was a 30 pixels jump as the star
passed the meridian, with a sudden 10 pixel jump occurring
during an 5min exposure. 

Looking back at the data, this has been happening every 
night of this run so far (whenever weather has been good 
enough to track targets over more than a few hours.)

Again, guiding seems to work perfectly well, so the
guider is likely not the issue.
 
The largest shift occurred at the star was passing HA=00:30:00.
The shift seems to be twice as large along X-axis (with star
drifting south) as along the Y-axis (with star drifting east). 

Something loose along the optical path of the camera?


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Submitted on 2012 Sep 22 [6:52:49]