Minutes of APO 3.5m User's Committee Phone Conference Monday, October 27, 1997 Attending: Rene Walterbos, Charles Corson, Bruce Gillespie, Ed Turner (Chair), Michael Strauss (taking minutes), Gene Magnier (substituting for Chris Stubbs), Jeff Secker Not attending: Alan Uomoto, Ed Kibblewhite Agenda: Upcoming Board of Governor's meeting (November 25) Director's Discretionary Time Instrument Policy State of the Observatory Post-shutdown Focus Changes Dust shutdowns ********Upcoming Board of Governor's meeting (November 25). What should Ed Turner tell them? Director's Discretionary Time: Suggestion out of September Sunspot meeting (see the minutes, apo35-general #193), is to allow up to 20% of the time for a combination of engineering and director's discretionary time (with the former taking priority in general, of course). It has not been thought through which kind of engineering time we're talking about: the previously scheduled, or the unscheduled (including emergency) time; we may want the 20% to be an appropriate average over a year. As the need for engineering time decreases, we may want to put a cap on discretionary time. However, it may be useful to allow the director to try more discretionary time to allow more innovative sorts of programs (such as target of opportunity programs, observatory-wide (as opposed to institution-specific) programs). Some brief discussion of possibility of gamma-ray burst follow-up program; Chris Stubbs is to write up a description of how such a program can be carried out. DD time could be used to recompense observers bumped by such a program. Ed should draft a specific statement of what the DD policy should be, and examples of how it would be used. This should then be posted to apo35-general to get the entire community aware of this, before going to the board with this. Instrumentation policy: the possibilities of giving instrument builders matching funds and/or observing time as an incentive. Also, policy towards visiting instruments; given the amount of observatory resources they use, should they be made available more broadly to the APO community? See the discussion on these issues in the minutes to the Sunspot meeting, apo35-general #193. Our instrumentation policy remains vague, and may need reworking. Most importantly, institutional shares in the telescope may have to be adjusted, through the board, with the arrival of each instrument; this is definitely going to cause trouble with the arrival of various new instruments down the road. The real problem is the dividing up the telescope into a series of separate slices of pie, one for each institution; there is no sense of benefit to the telescope as a whole. Gillespie: The UC Echelle is supposed to arrive soon. There is still no single point person on all of this, and it is difficult to find out what they are expecting of the site. And how will it be commissioned? As an baseline observatory instrument, the UC people expect that commissioning time will be taken out of observatory time, but the people on the mountain don't know any details of the UC commissioning plans yet. Ed and Bruce will contact UChicago to get more understanding of installation and commissioning requirements. ***************State of the Observatory Post-shutdown Gillespie: Telescope came out of shutdown with ~95% of the planned activities complete. Jon Davis will issue a shutdown report to apo35-general. Everyone is very happy with how things went. Anecdotally, observers have been much happier, speaking of successful runs. Corson: The main operational-relevant things that have been improved include: Secondary truss support Guider Rotator bearing and mounting Collimation of telescope Major problem these days: Focus has been drifting. This is probably not due to a single problem; some combination of mirror, secondary truss, and other components. The focus is sensitive to more than just temperature changes, e.g., wind direction. Truss has time constant of 1-2 hours, mirror is 20 minutes. But there may be some hysterisis in the system, things may change discontinuously. A "twang". Stubbs would point out that the thing to do is to have close-loop focus from the guider. It would take a few month to implement. Of course, this requires a properly collimated telescope, since you're focussing at the edge of the field. When to open the telescope? When outside temperature is below the internal dome temperature. Remote observers often forget this, and only *start* their dome flats after sunset. Remember that with 24 hour warning, the site can allow observers to use afternoon hours the vast majority of the time. Observatory attempts to open telescope as early as possible in general, unless otherwise instructed. More work is on-going to understand why the focus does what is it does, a number of things that need to be checked, temperature sensors, etc.; the guess is that in a quarter, things should be quite a bit better. A real-time imaging/video guider/acquistion camera would be tremendously valuable for focussing, acquisition of objects on a slit. Throughput measurement report is on the way from Corson and company; these confirm some degree of degradation (20% drop) since the realuminization. A possible problem: inaccuracies in the original throughput measurements, which were done with only a single star. **************Dust shutdowns Again, see the discussion of this issue in the Sunspot meeting minutes. Walterbos: There is too much tension between site staff and observers over the dust shutdown policy. There is a lot we don't know about this; keep in mind our aims are to maximize observing efficiency while minimizing telescope damage. Current estimate: 15% of otherwise clear nights over the last year were closed to dust. We are clearly not doing a poorer job than those observatories which do no more than go outside to shine a flashlight. We are not the only observatory that is actively worrying about this! e.g., the VLT will clean their mirrors *every* night. Walterbos: given the dust statistics, it seems that we are avoiding only of order 30% of dust exposure with our shutdowns. But is it not clear that all dust is equivalent; it may be, for example, that the dust we are measuring (~1 micron) is not as damaging to optics as dust of larger size, and the two may not be proportional to one another. We need a dust working group to think this through in some detail. Turner should go ahead to charter such a group in order to come up with some recommendations. Miscellaneous news: Rene Walterbos will have the archive of published papers from ARC in a week or so. Strauss has sent e-mail to all APO approved users who are not otherwise signed up to apo35-general, asking them to join; he has heard from ~1/3 of them. Strauss and Turner will discuss what to do about the other 2/3. The Sloan photometric camera has arrived, and has been successfully bolted to the telescope. See the reports and photos off the ARC home page. Last meeting minutes are approved. Next meeting is Monday, November 17, 1997. 12:30 EDT APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 204 in the apo35-general archive. 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