MDM Trouble Report for 2013 Sep 01

Telescope: 1.3m
Observer(s): Halpern (Columbia)
Instrument: Nellie

Problem(s) Encountered:
Same two problems as last night:

A round drop of water on the dewar window.  Even though I 
was able to keep it dry during the day with a single
15 minute flush of N2, a central condensation formed soon
after opening at night.  Flushed it once again, but the
droplet came back after an hour.  This is difficult to
understand, as the humidity was only 67% on the weather
station, and similar to KPNO's.  It appears from last night
and tonight that several hours of observing are not enough
to dry it out, leading me to suspect that some other effect
is in play.

The N-S oscillation appeared as soon as I started observing at
+76 declination.  I didn't see it at other positions, but I had
relatively little time on other parts of the sky during the
two partial nights that I was open during this run.

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Submitted on 2013 Sep 2 [1:29:59]