MDM Observatory 2.4m Telescope Observing Report for 2010 Dec 30

Observer(s): Jules Halpern, Jia Liu
Institution(s): Columbia

Instrument: OSMOS

No Observing (see comments below)
Conditions were Non-Photometric most of the night.
Problems were encountered, see the separate trouble report for details.

Seeing and Weather:

Observing Summary:

KPNO telescopes are closed due to ice on domes.
MDM telescopes are also closed.
Setting up for our first run with OSMOS.
See questions below.

1.  Dome stuck in ice?

Paul couldn't turn the dome in the afternoon evidently due to ice.
I couldn't turn the dome at the beginning of the night either.
Trying again after a few hours, I got the dome to make some
jerky movement in one direction from the home position, but not in the
other direction.  Evidently it is still bound by ice.  Not wanting
to risk breaking anything, I gave up on the idea of observing tonight.
Hopefully the sun will melt the ice tomorrow, although the forecasted
night-time temperature is just as cold for tomorrow.

2.  Condensation on dewar window?

Taking MIS flats with OSMOS, I see that a refractive looking feature
has appeared in the exact center of the image.  It is round, about an
inch in diameter.  This is new since yesterday.  Undoubtedly it is 
condensation on the CCD dewar window, also caused by the weather.
If this doesn't resolve itself tomorrow, is there a way of blowing 
dry nitrogen across the dewar?  I see that there is a round cover
plate on the bottom of the spectrograph, but I won't open it without
authorization.

3.  Focus camera and/or collimator?

Temperature is very cold at the beginning of the night, about -7.3 C.
Is it colder now than during any previous run with OSMOS?  Taking the
advice of the OSMOS manual that says the camera focus is a function
of temperature, I refocused it using the Sieve Mask with no disperser,
to project what looks like a single round hole onto the CCD.  Trying
to get the sharpest image leads to a camera focus of about 6550 microns,
which is consistent with the advertised +350 microns per 10 C decrease.  
I didn't do anything with the collimator focus, as I can't find any
instructions about that.  I'm not sure why the focus of the camera
changes but not the collimator.  Any explanation of this would be
appreciated.

Using the 1.2 arcsecond slit, the spectral FWHM is about 4.1 pixels in
the inner slit, and 2.8 pixels in the center slit.   If this is typical
I guess it's okay.  But I wonder if a different focus position for the
collimator would improve the FWHM for the inner slit at the expense of 
the center slit.


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Submitted on 2010 Dec 30 [23:58:38]