MDM Trouble Report for 2010 Dec 3

Telescope: 1.3m
Observer(s): Skowron (OSU)
Instrument: CCDS

Problem(s) Encountered:
Dewar of CCDS was not filled completely (at 6pm) which lead to high background 
and temperature of the detector going up from -109 to -57 until the 
dewar was filled up completely (9pm).
Background on bias images raised from 115 to 160 counts.
After 1.5 hour from filling the dewar up, temperature dropped back to -109.

With high background some black spots on ccd appeared to be visible,
they vanished when background dropped. Spots looks like some 
debris which fallen into instrument. Hard to say when, as they are not 
visible in normal conditions.

Similar spots are visible on acquisition camera with long exposures (~ 25 s),
or shorter exposure but with ambient light falling into the dome (eg. open doors) .

Today the tank on the platform has been replaced to the silver one.
This one, it seams, has a slightly different rubber pipe than the
white tank, which is not freezing enough and is still a little bit 
flexible. During the filling the pipe slightly moves and can slight out.
I could not noticed that and assumed that dewar is full cause LN was 
pouring onto the floor. Also possible is that too high inflow, of 
the LN to the dewar, forced part of liquid flow outside. 
Something similar happened in the morning, and closing the valve a little bit 
seamed to help (or rotating the end of the pipe).

Also it feels that the pipe from silver tank is slightly harder to insert 
all the way in. Something is catching it 0.5 inch before.


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Submitted on 2010 Dec 4 [6:25:47]