Detector

Early in the semester one of the MOSCA CCDs (CCD #19) produced an intermittent fault, where on the telescope it would only work at certain rotator angle positions. After a full check of the controller and all external cables it was decided to open the cryostat to make a inspection of a suspected wiring fault to the detector, but nothing was found. After mounting the instrument back on the telescope to check if the fault persisted it was found that CCD #19 worked but now CCD #15 did not work at all. Investigating this on La Palma and later in Copenhagen, it was found that both amplifiers on CCD #15 did not work and the CCD is effectively dead.

Fortunately, there is a possible direct solution to this by using the old ALFOSC CCD #7 as replacement. We already have permission from the `Instituto de Astrofísica de Andalucía', who are the owners of this CCD, to use it and Anton Nurop Sørensen has agreed to replace the CCD in the near future and we hope to have the instrument back at the telescope in the second half of December. There are two observing runs scheduled with MOSCA before that time, but both these programs can basically just as well be executed with ALFOSC and the PIs have agreed to the proposed change of instrument.