It came to my attention last week during an observing run that the DIS only exhibits a bias pattern while mounted to the telescope. I see no discussion of this on this web page, and was wondering if this is a well known fact? I took some unmounted biases for my run and they were some of the best bias frames I've ever seen! It seems obvious that the bias pattern is produced as a result of the coupling to the telescope. It seems to me like this would be much easier to fix than an actual problem with the camera electronics. Is there some way that we can isolate the camera from the telescope? I should point out that the DSC bias frames are also worse when mounted to the telescope. The difference is not quite as obvious for the DSC as it is for DIS, but it is still there. Gordon APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 25 in the apo35-dis archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-dis/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-dis@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO