Removal of cosmic-ray events in spectroscopic CCD data

Current methods of treating cosmic-ray events in CCD data images often fail for a variety of reasons. Cleaning of cosmic-ray events from multifiber spectroscopic data is particularly difficult due to the variation in fiber response between exposures. With the development of large fiber systems [such as the 2 degree field (2dF) project on the Angle-Australian Telescope (Taylor and Gray 1990, Proc. SPIE, 1236, 290)], interactive cleaning of data frames is becoming the most time-consuming task in reducing data. The advantages and disadvantages of some of the current non-interactive techniques are discussed, with particular emphasis towards cleaning multifiber data. In order to improve the detection and removal of cosmic-ray events, a scaling technique that provides a better match between repeated frames has been developed. This technique has been used to create a new cleaning program that has a number of improvements over currently available programs.