Hello, As you may already be aware, recent DIS throughput measurements indicate that there is a very real difference in throughput between the medium-resolution red grating and the low-resolution red grating. However, the extreme wavelength range of the low-resolution grating still leaves much of the chip unused. Therefore we will be sticking with the "default" setups that were established when DIS II was checked out last spring: high/high in one bay, and blue low/red medium in the other bay. You may still request another pair of gratings (one blue, one red) if important for your science, but please be sure to notify us of your request at least a few days in advance of your run. If your request conflicts with the program of another observer on the same night who wants one of the default setups, you will have to sacrifice half an hour per grating (one hour for a grating pair) to allow them to be changed in the middle of the night. Last-minute requests may also incur a time penalty, or may be refused. Please do NOT assume that your proposal constitutes sufficient warning that you want a non-default setup. The inconsistencies in filling out the proposal form that were discussed recently by Ed Turner also cause us some confusion about DIS grating requests. So we will continue to assume that you will be using one of the default pairs, unless we are explicitly informed otherwise by email to obs-spec@apo.nmsu.edu . This is the same policy that was articulated in more detail in apo35-general message 563 and has been in practice since then. The only difference is that in March we were anticipating that we would eventually be able to retire some gratings, whereas now it appears that there are continuing reasons for some programs to require non-default sets. Plots of the throughput results are available on Jon Holtzman's pages: > You can see the relative throughput plot at: > http://ganymede.nmsu.edu/holtz/rel.gif > and the absolute plot at > http://ganymede.nmsu.edu/holtz/t.gif Thanks for the cooperation you've all given us in the past few months while we tried to work out a reasonable policy! Russet McMillan. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 614 in the apo35-general archive. You can find APO the archive on http://www.astro.princeton.edu/APO/apo35-general/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-general@astro.princeton.edu APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO APO