Minutes of APO 3.5m User's Committee Phone Conference Monday, January 6, 1997 Attending: Bruce Gillespie, Ed Turner (Chair), Michael Strauss (taking minutes), Rene Walterbos, Julie Lutz Given the small number of people attending this meeting, we decided to have an abbreviated meeting, and spent most of the time discussing the telescope shutdown, which is a few days from ending. This shutdown was to realuminize all the mirrors, and to replace the enclosure wheels. Gillespie: The APO staff is putting everything back together today, rough alignment in progress, with full alignment and pointing model (probably requiring 1.5 nights of clear skies) starting tomorrow night. The earliest the telescope could be given back to the scientists for observations is thus Wednesday or Thursday night, but the mountaintop is in the middle of a blizzard right now, and so there may be further delays. One enclosure wheel was replaced about 9 months ago; during the shutdown, the other three enclosure wheels were also replaced. It was anticipated that this would be more difficult, given the fact that some of these wheels had drive motors on them, but all went very smoothly. Many kudos to Jon Davis and his group, who were able to do the last three wheels without help from L&F. All three mirrors have been realuminized, at KPNO (primary) and Sac Peak (secondary, tertiary); the reflectivity from each as a function of wavelength looks beautiful. Kudos to Mark Klaene to making this all work. When the primary was taken out, it was noticed that some of the ventilation tubes that force air through the cells in the back of the primary were loose; the epoxy that held them in place had come loose. It turns out that fixing them properly would have been a major job, and therefore the decision was made simply to take the loose ones out altogether pending a redesign. If that turns out to degrade the seeing, then something will have to be jerry-rigged to put them back in. It is expected that a better system for attaching the tubes to the primary mirror cell will be developed and implemented at some future date. When the secondary was taken out, it was noticed that the flex-joints for the whiffletrees connected to the secondary servos were all broken. These have now been replaced. The secondary support system may need to be replaced with a different design in the future. It was also noticed that the piezoelectric stacks for the secondary, which are in place for future tip-tilt work, had all failed, and will need to be repaired, and have been replaced by dummy cylinders for the time being. As soon as there is some clear weather, new throughput measurements will be taken. Everyone is hopeful that with the realuminization, the throughput will have gone up substantially. The primary mirror support system is in the process of being redesigned for higher bandwidth and better stability, with the aim to reduce low frequency mirror oscillations. The new system should be in place on a 1-2 month timescale, and will not require any major telescope shutdown while it is in progress. Thermal sensors in the mirror have been replaced by Alan Diercks. During the shutdown, Jon Brinkman and Alan Uomoto worked on the DIS electronics, and are close to eliminating a source of AC pickup in the CCD's; they are waiting on one new part. Charles Corson, previously of KPNO, is joining the APO 3.5m staff. Progress has been made on finding a vendor for polishing the new secondary; we are talking to several different vendors. We should be closer to making a decision in about 3 weeks. There will be a four-night block of time given over to engineering in late January. It has been scheduled for installation of the new guider and to work on the primary support system. We will make a larger effort in the future to send out information to the user community about what actually happens during these engineering runs. Last meeting's minutes are approved. Next meeting, February 10, 12:30 PM. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 113 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