Minutes of APO 3.5m User's Committee Phone Conference April 8, 1996 Attending: Alan Uomoto, Bruce Gillespie, Ed Turner (Chair), Lew Hobbs, Roger Hildebrand, Michael Strauss (taking minutes), Rene Walterbos, Alan Uomoto, Julie Lutz, Chris Stubbs Agenda: Current status of Echelle Plans for realuminizing the primary Optical throughput of telescope/instruments Recent engineering projects done by UWashington and APO people Preliminary thoughts for a JHU/UC/ARC instrument What is the current status and installation plan for the Echelle? Hildebrand: Last summer ran into a serious vacuum problem, leading to major redesign. New camera tank being fabricated, ready early May; 6 weeks of testing of this tank, then mount CCD in camera (will relevant manpower be busy with Sloan camera?). Six weeks of further testing. Following this schedule, the Echelle could be delivered in October. Now at high confidence that this *will* be completed successfully. Just about everything with the instrument is being rebuilt from scratch. One small issue: The Chaos laser is currently sitting at the port at which the echelle will go; the Echelle and Chaos people need to coordinate this. It is not yet clear how much time commissioning will take. One potential problem is that Bob Lowenstein, whose expertise will be critical during commissioning, is planning a several-month trip to the South Pole around October, which could delay things several months. With this in mind, the UC suggests that proposals not be accepted for survey instruments until the quarter *following* the declaration that they are successfully commissioned. We also recommended that the commissioning time for this instrument would come out of engineering time (i.e., it would be shared between institutions, and not just come out of U Chicago time). The HRI (High-Resolution Imager) is not currently being worked on; there are no plans at the moment to reserrect it. Plans for Coating the Mirrors Given the fear (see below) that the mirror coatings are causing significant loss of reflectivity, especially in the UV, we are looking to do recoating of the primary in late June at KPNO (our next opportunity would be October). There may be a conflict with the need to get the 2.5m mirror coated; if so, the 2.5m mirror could perhaps be done at McDonald. Decision will be made early May, depending on the details of McDonald's setup. This will of course have an effect on the telescope schedule. Secondary and tertiary coatings are bare aluminum. More sophisticated coatings have better reflectivity over large wavelength range (down to 3500 A) and are easy to clean. We might look into this. Optical throughput of the telescope/instruments Tonight (4/8), there will be a run measuring throughput of DIS in some detail (see telescope logs for the results of this run), to be carried out by NMSU personell. This is engineering time. Will follow Jim Gunn's suggestions for tests of throughput. Tests of slit masks as well. Jim Gunn suspects that the throughput problems are related to mirror coatings, especially in blue. Observatory reflectometer only works in red. Multiwavelength devices don't exist. Jim will design a device to do this; APO is offering to build it. Spectrophotometric calibration device now is at APO for measuring throughput of MT; use it for 3.5m as well! We did not get a chance to discuss options/plans for new slits for DIS. Engineer projects--recent work done by the "Improvements" group at UWash, APO. Bruce Gillespie: Last week of engineering time: new, stronger rotator motor has been installed (this motor has overcurrented; problems are not over yet). Tightening of secondary vanes has changed the focus as function of altitude has changed; data were taken to recalibrate this, and the run of focus as a function of temperature. This should allow a better automatic focus adjustment. Ideally, we could have a semi-automatic mechanism by using the guider to continually measure focus (and seeing, of course), and update pointing model as well. Chris Stubbs: Telescope vibrations: instability in telescope servo systems and wind-driven oscillations are important contributors to seeing. Secondary vane tightening seems to have improved the oscillation problems. Fixes to servo problems are in progress. There is some evidence that the 20 Hz vibrational problem is much reduced. Progress on reducing the effects of scattered light is going slow, due to lack of manpower. The worst of the enclosure wheels was successfully fixed. It would take a 7-10 day shutdown to fix the other three wheels (perhaps this could be done during realuminization in late June?). How do we know that secondary is really at fault in optics? The best way to do this is to do an optical test of secondary; take it off the telescope and ask someone to map it. The test of rotating the secondary 120 degrees would be inconclusive, given the inherent noise in the Hartman tests. We could do this while primary is recoated in late June. Preliminary thoughts for a JHU/UC/ARC instrument Alan Uomoto summarizes discussions at JHU about this instrument: instrument should be capable of unique science, must have JHU interest. Should it be a key project kind of instrument? Current favorite idea is a wide-field (12-15') low dispersion (R = 1000) high throughput multiobject (40) spectrograph. Using aperture masks, not fibers. Larger field of view than instruments on Gemini, Keck. Wavelength coverage 4000-7500 A in one shot. Think of this as a Sloan followup instrument. Can use Advanced Camera CCD's (2048x4096). This is one of a few options still being discussed. Chicago is interested in add-on instruments for Chaos. Time to get input from whole APO community; Alan will put together a several-page description of their idea for comments from everybody. Finally, it was decided that the APO community should have the opportunity to comment on the minutes after they are posted, to correct any technical mis-statements. People should send corrections and/or comments to Michael Strauss (strauss@astro.princeton.edu) or to apo35-general, and the appropriately corrected minutes will be approved at the start of each User's Committee meeting. Next meeting, May 13, at usual time. Two items for the agenda next time: o data archiving at APO--is a minimal semi-automated archive of image data at the site worth the cost and added work? Something on the scale of the "Save the Bits" program at KPNO. Recently, people have lost data by improper ftp'ing. o Network and remote interface problems and enhancement plans. The NSF has recently put out a call for proposals for netwrk/throughput-related issues. Don York may already be on this. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 58 in the apo35-general archive. 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