MDM Trouble Report for 2007 Sep 16

Telescope: 1.3m
Observer(s): Eastman & Prieto (OSU)
Instrument: 4K

Problem(s) Encountered:
At 12 am, when the humidity reached 90%, we closed the dome, 
dark hatch and mirror cover.

At the end of the night (4 am), when the humidity was 85% and 
dropping fast, we re-opened. When we took our first image, 
there was a bright ring in the center of the chip, with a 
diameter of ~1600 unbinned pixels. The ring was about 
~20% too bright and just inside the ring was ~20% too faint.

Worried that it might be condensation, we inspected the primary 
and secondary mirror, as well as the telescope truss, but none 
showed any sign of moisture. Next we moved an empty filter into 
position and looked inside the telescope to see the 
condensation on the dewar window.

Looking back through our images taken before we closed, we saw 
the beginning of the condensation at 11:39 pm, when the humidity
was at ~87%. We didn't see it at 11:14 pm, when the humidity was 
85%-86%.

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Submitted on 2007 Sep 17 [5:53:16]