MDM Observatory 1.3m Telescope Observer's Report for 2006 Mar 07

Observer(s): Denney/Bentz/Jiang
Institution(s): OSU

Instrument: CCDS

Worked for 4.5 hours (first half of the night)
Conditions were Mixed most of the night.
Problems were encountered, see the separate trouble report for details.

Seeing and Weather:
   Clouds from 1:00 until 7:00.
   Beg: Clear, Winds Calm
   Mid: Cirrus, Winds Moderate
   End: Patchy Clouds, Winds Moderate

Observing Summary:

Tonight we were plagued with instrument issues, mostly readout errors with CCDS.  We didn't actually get any errors from Prospero, but our data was bad.

We were getting the same type of readout errors as we've described previously, with arc lamps that suddenly start moving diagonally across the display.
We also experienced salt and pepper noise in our spectra that wouldn't go away regardless of what we did.  I'll explain more about our trouble shooting in the trouble report.

Also, we had an additional problem that we spent 4 hours this afternoon trying to fix.
Some type of light leak/reflection appeared in our blue spectrum, centered at 4250A.
The reflection appeared as a bright band around 4600A.  
It stayed at this wavelength while the center wavelength of the grating ranged from 4250A-4550A.  
We never determined the source of this light leak, but avoided it by shifting our center wavelength down to 4200A instead of our ideal 4250A.
I'll describe more about what we tried to trouble shoot in the trouble report.

Even though our spectra were junk, we continued taking them, because we didn't know what else to do, and we actually had a couple hours of clear skies.
Finally, after about eight bad images, they all of the sudden just got better, for no apparent reason.
Although we had previously tried cycling the power to the instrument as well as the computers, this didn't work, and we have no idea why the images just starting looking good.
We then re-exposed most of the previous images that had been bad, obtaining 13 good spectra before the problem suddenly reappeared.

At this point, the humidity was rising and the dew point was approaching the outside temperature, so we stopped trying to retake AGN spectra that were bad, and started our Standard Star Observations.
We took 3 out of 6 of these observations without incidence, but then we got a new problem.  The 4th-6th images suddenly had a chunk almost completely blocked out (i.e. zero counts) on the left edge of the spectra.
We have no idea what caused this and it was different that the previous errors.  We finished our observations with these errors anyway.

We then closed up about 12:30 because clouds were coming in, and we were losing our guide star.
Plus, the dew point was coming close to within 4 degrees of the outside temperature, and we knew we wouldn't have enough time for another object, readout errors or not, before weather conditions forced us to close.

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Submitted on 2006 Mar 8 [4:54:57]