The ROTSE-III system runs with an unfiltered, thinned CCD. This, combined with the wide-field, creates difficulties in getting good quality flat-field images. Not only do we have to deal with the vignetting from the wide-field and the pixel-to-pixel quantum efficiency variations,7.1 strong night-sky emission lines create an unpleasant interference fringe pattern in the images. The final plan for obtaining flat-field images will most likely change from the process currently described in this chapter.
For use in the automated pipeline, calibration files are put in the directory: