MDM Observatory 2.4m Telescope Observing Report for 2009 Dec 04

Observer(s): zhu,zhao
Institution(s): university of michigan

Instrument: TIFKAM

Worked for 16 hours (all night)
Conditions were Mixed most of the night.
No equipment or software problems were encountered.

Seeing and Weather:
   Clouds from 12:00 until 4:00.
   Beg: Seeing 1 arcsec, Clear, Winds Calm
   Mid: Seeing 1 arcsec, Patchy Clouds, Winds Calm
   End: Seeing 1 arcsec, Overcast, Winds Calm

Observing Summary:

Starting with a clear night, we obtained several photometric data. 
The seeing throughout the night is excellent <1  all the night.But clouds 
gradually cover all the sky by 4 am and we are unable to take photometric
data then. When we tried to take sky flat this morning, TIFKAM image has a 
dark patch in the middle which looks like some sort of occultation. But we 
don't have any occultation through the optics. After we close the dome and the
telescope,this occultation disappear. We don't know why. Our only explanation
is that RETROCAM moves out slowly after we took the Ar spectroscopy lines.  

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Submitted on 2009 Dec 5 [7:58:50]