MDM Observatory 2.4m Telescope Observing Report for 2017 May 26

Observer(s): Halpern, Cho, Collver
Institution(s): Columbia 

Instrument: OSMOS

Worked for 9.5 hours (all night)
Conditions were Photometric most of the night.
No equipment or software problems were encountered.

Seeing and Weather:
   Beg: Seeing 1.1 arcsec, Clear, Winds Moderate
   Mid: Seeing 1.1 arcsec, Clear, Winds Moderate
   End: Seeing 1.1 arcsec, Clear, Winds Moderate

Observing Summary:

Eric cleaned the entrance window of the B4K detector today.
I will report on whether it helped after I look more closely
at the flat-field images.

A good night of imaging with OSMOS.  The dome azimuth behaved well,
as did the pointing of the telescope.  One anomaly that I don't
understand is that imaging with g, r, i filters required *very*
different telescope focus, for example:

g  2684
r  2668
i  2678

This is not supposed to happen with OSMOS, and indeed I never
noticed a significant difference before, e.g., when I used the
same three filters in September 2016.

Maybe I will test V, R, I the next night for the same effect.

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Submitted on 2017 May 27 [5:48:42]