I am happy to announce that the blue side of DIS has been returned to service and is expected to be ready for on-sky science use tonight. We were fortunate to be able to get a replacement chip very quickly and thus the down time was at the very minimum end of the range anticipated when the old chip was damaged (see apo35-general message #570 issued on April 26). Additional good news is that the new chip is of somewhat better quality than the one it replaced, having better cosmetic quality and slightly better QE than the old chip. Its read noise is the same, about 4-4.5 electrons. Furthermore, the improperly AR coated field flattner lens in the DIS blue camera has been replaced with a new and correctly coated one. This will restore throughput between about 3800 and 4600 Ang. See apo35-general message #559 for a description of the problem with the old lens. Thus, although there remain some relatively minor electronics enhancements and debugging to be done to achieve optimal performance, the DIS upgrade and repair is now essentially complete. Both the APO staff and the UW engineering group have worked hard to achieve this very considerable success and deserve the thanks of the user community. I would very much like to see comparison spectra taken of the same (non-variable!) object with the same exposure time and under similar conditions with the old and upgraded DIS. If anyone obtains such, please provide me with copies of the spectra if possible. Ed Turner APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 580 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