APO 3.5-m Telescope, Instruments, and related systems Status: 10 September 1995 Telescope- Attention was paid to the various telescope and enclosure drives this past month. A problem with the azimuth drives was solved by changing a parameter in the controller, eliminating frequent motor stoppages due to overcurrent. The altitude drive continues to have an intermittent offsetting problem, which is under investigation. The more recent pointing models show ~3 arcsec rms blind pointing, but actual on-sky performance is sometimes inconsistent. The enclosure drives continue to lose the tuning of their servo adjustments on a weekly basis--an engineer from the company that built the enclosure drives is being brought to the site to make a diagnosis. Nasmyth rotator stalling problem was solved by installing a new stronger motor. The primary and secondary mirrors were both recollimated during engineering time. Image quality continues to be tested, and recent data show slight but noticeable astigmatism in the Nasmyth images which has not been seen before--this is to be confirmed through a Hartmann test this coming week. Also, since instrumental/system throughput has been under question, the reflectivity of the three mirrors were checked, showing a net reflectivity of the telescope of ~60%, nominal being ~73% for fresh coatings. Many people too numerous to list helped with the testing and repairs of telescope, including site staff but also many research staff and students from the ARC member institutions. As a case in point, Ed Kibblewhite and his students from UChicago analyzed recent data taken with their adaptive optics package (ChAOS), and discovered a strong image motion resonance at 20Hz. Not knowing if this signal was internal to their instrument or in the image itself, tests of the telescope were performed which measured image motion with the ChAOS package, plus monitoring mechanical motions of the telescope itself. The 20 Hz motions were found to be in the telescope, and are being driven by the altitude velocity servo which updates its input to the motors at 20 Hz. How this 20 Hz image motion effects the point spread function is presently being tested, and we have some optimism that a straightforward fix may correct this problem. As reported last month, we found that the circumferential cracks in the enclosure wheels had grown in the past year, and a campaign to replace these wheels at the earliest opportunity has been launched. One replacement wheel has been ordered (made with a slightly different steel), and in parallel we are exploring a new wheel design that has been suggested by L&F which may be better, cheaper, and faster (or at least better and cheaper). Replacement of the worst cracked wheel is planned for late October, but if any wheel crack accelerates or chunks break out of the wheel before the planned repair, the telescope will have to be closed. The experiment to test laser-cleaning of mirrors continues. Routine measurements of r-naught and cloud scanner images of the sky continue. A recent all-sky "movie" of a dark night is available from our web server. INSTRUMENTS (general) Jon Brinkmann will take the post of Scientific Instruments Engineer, arriving at APO this week after a brief swing through Chicago to talk with the GRIM2 developers Mark Hereld and Bernie Rauscher. Jon will initially be tasked with projects related to instrument calibration systems, the guider, and telescope baffling. As promised, instrument reports have started to appear in the APO e-mail exploder--see the APO web server for information on how to subscribe to the service. DIS- Karen Gloria has written a detailed status report on DIS and placed it on the e-mail exploder last week. Of note, the bias/gain shift of the red camera seems to have stopped since early summer, possibly as a result of Richard Lucinio's attentions in June. The question of DIS throughput is being studied by several investigators. Jim Gunn was at APO this past weekend and attempted a DIS spectrophotometric measurement but was hampered by clouds. He has promised to send us a prescription for making this measurement, which we will attempt during engineering time. If other scientists have proposals to measure DIS (or any instrument) performance for the benefit of all, we will gladly consider those programs as candidates for engineering time. GRIM2- The instrument has been behaving very well. Nothing to add to last month's report. DSC- Pretty much unchanged since June, with the exception of some additional tests and baffling which improves stray-light rejection of camera when mounted at Nasmyth. Echelle- Return date to APO is TBD. Not to be scheduled in upcoming quarter. HRI- Return date to APO is TBD. Not to be scheduled in upcoming quarter. Guider- Closed-loop tests done in past week, results will be published. New s/w from vendor received which was supposed to fix run-time routines, compiled but didn't execute. Trying to get 512^2 chip at the site which has better noise and sensitivity, and send 1024^2 camera back to vendor for overhaul. Also trying to get Eric Deutsch's utility on-line for finding bright guide stars for any target. ChAOS- Used successfully for engineering studies of telescope vibrations and measurement of wavefront. Results to be available shortly. Calibrations- Schedule for this project is TBD, but the initial capabilities were expected to be ready by now, but have been delayed by repair work on telescope and enclosure drives. S/W and network- Have had a few days of unreliable network access, again appears to be related to routers in the Washington DC area. A backup modem capability has been implemented at the site, but to be fully useful requires certain s/w and phone lines need to be installed at the remote sites. Jim Fowler has sent instructions to users, but no one appears to have yet implemented modem capability at the remote observing rooms. Bruce Gillespie APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 15 in the apo35-general archive. 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