MDM Trouble Report for 2017 Dec 10

Telescope: 2.4m
Observer(s): Jessie Runnoe, Mike Eracleous (Michigan, Penn State)
Instrument: OSMOS

Problem(s) Encountered:
We encountered the same problem reported by Justin Rupert  on 
2017 December 8. We saw the icicles show up in the internal flats 
taken at the beginning of the night (with ROI 4k x 1 k), even though 
the count rate was not high enough to saturate the detector. Running 
snapclean did not seem to fix the problem. In fact, it was not clear if 
snapclean was running at all since it did not change the ROI to 4x x 4k 
as expected. We tried changing the  ROI manually to 4k x 4k and then
running snapclean, which gave us a good flat in the 4k x 4k configuration.
Switching back to 4x x 1k brought the icicles back. They seem to occupy
a smaller area at shorter exposure times but they are still there. Since the
weather was bad, we did not really lose time but we were not able to get
useable flats.

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Submitted on 2017 Dec 11 [3:59:03]