Quality control

New non-linearity correction coefficient images were made available for download from the NOTCam calibration archive. Testing the old coefficient images on new data shows that on average the behaviour is the same, the main difference being individual pixels that are differently affected by dust on the detector since cleaning the array in January of this year. In the new version of the IRAF package ``notcam.cl'' a script is available for doing the non-linearity correction pixel by pixel on the raw images.

A distortion correction for the Wide-Field camera was made on very good data of a dense stellar field for J, H and Ks. This model has been tested on many datasets from earlier and later dates. In all cases, applying the model improves the images substantially, though in some cases better than others. It is not entirely clear why the correction works less well for some data, as no direct correlation is found with, e.g., rotator position or airmass.

Distortion correction for the new filters Z and Y has not yet been made, although it seems viable to use the J-band model for these two bands.

The twilight flat archive is being continuously updated.