Detector

The mounting system for the pressure sensor was replaced with electrically isolating pieces to eliminate the noise induced by the actual sensors, so we can now monitor the pressure while operating the detector.

A problem with the charge-transfer-efficiency of the CCD at low light levels was found. This was detected when averaging a few hundred 30-sec exposures, where specific columns show the signal to be smeared out along the column. This is not visible in the individual spectra, while spectra with stronger illumination this effect is not visible either. As far as we can tell, this effect is stable in the detector and seems likely to be feature of the detector itself. In this specific case, the data can be (partly) corrected while in most cases the effect will not be detectable. However, we need to substantiate this in more detail and define under which circumstances this might effect observations. As this might be something intrinsic to this type of CCD and given that the FIES CCD is similar we will check if this effect is present as well. We do note that given the type of observations done with FIES we do not expect this to have any effect on the data.