I discovered some strange behavior of the DSC when I took bias frames last night, at a variety of telescope positions. It appears there may be some effect that depends on the position of the telescope. You can read about the problem, and see a picture, by looking at URL: http://www.astro.princeton.edu/~richmond/dsc_mosaic.html I hope that someone can explain it.... Michael Richmond APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 38 in the apo35-dsc archive. You can find APO the archive on http://astro.princeton.edu:82/apo35-dsc/INDEX.html APO To join/leave the list, send mail to apo35-request@astro.princeton.edu APO To post a message, mail it to apo35-dsc@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO