I do not understand. The blaze on very fine gratings is not so good as on coarser ones, but the performance on both med and high is terrible. That on low is fine, so the detector is not at fault, but it is not so bad that the grating could be in backwards. I will look when I am there if there is any time. jim APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 47 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