MDM Trouble Report for 2005 Nov 2

Telescope: 1.3m
Observer(s): Martin Bureau , Anne-Marie Weijmans (Oxford University, Leiden Univ.)
Instrument: Direct Imaging, f/7.6, echelle

Problem(s) Encountered:
We repeatedly had problems with the bias level of the CCD. Many
exposures had a substantial number of bad rows, so much so that many
exposures were useless. Although we have no proof of this, it seems
that doing a  df  helps to solve the problem. A total of at least 10
images were affected during the night, for a total of about 2 1/2 to 3
hours lost during the night, as well as most of the biases we
attempted to take at the end. Some of the affected images might be
salvageable, since the bad rows are also present in the virtual
overscan region and subtract out (e.g. with  colbias  in IRAF), but
the boundaries of the bad regions remain, so this is only a partial
fix.

The images concerned can be found in
/data/tambora/obs13m/Direct/051102/051102_*

All of the following images are affected to various degrees:
034-035,037-038,041-043,046-047,050-051,067-076

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Submitted on 2005 Nov 3 [8:13:43]