MDM Observatory 2.4m Telescope Observing Report for 2015 Dec 21

Observer(s): Y. Jeon, Y.-K. Sheen, D. Park
Institution(s): Seoul National Univsersity

Instrument: OSMOS/B

Worked for 9 hours (all night)
Conditions were Overcast most of the night.
Problems were encountered, see the separate trouble report for details.

Seeing and Weather:
   Clouds all night.
   Beg: Seeing 1.7 arcsec, Patchy Clouds, Winds Light & Variable
   Mid: Overcast, Winds Moderate
   End: Clear, Winds Calm

Observing Summary:

We started tonight with partly cloudy sky.
The seeing was 1.7 arcsec at the begging.
Clouds were getting worse and, 
after midnight, the whole sky was covered with thick clouds. 
At 3:30AM, we cannot see any guide stars and 
we closed the dome. 

We have several problems. 
1. At the begging, we set the RA/Dec encoder with a bright star 
near the zenith. Then we found that the Airmass term in the TCS monitor 
showed about 1.5. We checked the telescope and 
it pointed near the zenith. We did not figure out why this happened. 
After we set the zenith with tilt sensor numbers, this problem was gone. 
2. At first, we could not see that the Epoch on the TCS monitor 
had a value of 2015.0. With this value, the pointing was always trouble 
when we pointed different bright stars. 
After I changed this value to 2015.9 with ‘TCS Equinox’ button 
on the xtcs, this problem was solved. 
I heard that previous observers had a pointing problem during their run. 
It might be because they used the Epoch as 2015.0. 
3. The Xe lamp did not work at the beginning of the night. 
If we took arc frames with Xe lamp, there was no emission line from Xe. 
However, we could get the arc data from Xe at 3AM. 
I’m not sure why the Xe lamp did not work at the beginning. 


We have several comments. 
1. The dog barking sound when an exposure is finished was very useful. 
2. The new tilt sensor value 009,-003 is quite accurate than previous values. 




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Submitted on 2015 Dec 22 [3:43:27]