Apache Point Observatory 3.5m User's Committee Meeting August 30, 1999 Attending: Jeff Brown, Rene Walterbos, Bruce Gillespie, Ed Turner, Michael Strauss, Chris Stubbs, Alan Uomoto. Not attending: Ed Kibblewhite. Outline: Hiring of Observing Specialists 3.5m Shutdown status Woodgate's Fabry-Perot instrument Miscellaneous ******************Hiring of Observing Specialists********************** Gillespie: Lisa Wells, whom we hired as an observing specialist, has had a chance of heart; she has accepted a job at another observatory. We have hired a new person, Frank Deglman, who will show up in the first week of September. We hope he will be able to solo on the telescope near the end of September or early October. *********************Shutdown Status**************************** Highlights: A dozen temperature sensors are bonded to the primary, which we've decided to remove, concerned about thermal cycling causing strain in the glass. The removal of the first of them took a piece of glass along with it, the size of a lima bean, off the side of a cell wall. There is a small crack in the glass, which may propagate further, so everyone is concerned. After much agonizing and careful investigation, there may be stress (with temperature cycling) on the glass from the bonding of the other sensors to the glass, and so the recommendation is that they all should be removed, although it is unclear whether this needs to be done immediately, or could wait to a future shutdown. Uomoto: This sounds familiar; I've done similar things, and have had similar problems. The epoxy bond is stronger than the glass itself, so taking these off inevitably causes troubles. A consultant from the Steward Mirror Lab is coming out here September 7 to give us some advice. We may lose another week to this problem, which we *hope* we can make up some of the lost schedule by shortening of the overhead for telescope collimation, etc., following the shutdown. We agreed that the immediate concern is the existing crack. The other 11 temperature sensors have been there for about three years, without any obvious damage, so the removal of them is less urgent. Other shutdown tasks accomplished thus far: o Rebuilding of water coolant system on guider and rotator. o Replumbing of bellowframs in the primary mirror cells, 10% of which needed repair or replaced. o Tertiary mirror has been realuminized. o The new secondary will be coated about mid-week, and installed above five days later. o We'll wash the primary. *********************Miscellaneous***************************** Bruce Woodgate will bring his instrument (Fabry-Perot imager, resolution 4-28 Angstroms; 3.3' field-of-view with 0.18" pixels) to the site in the fourth quarter. It could be made available to the APO community as a whole for at least the calendar year 2000, for six nights of telescope time (from Director's Discretionary time). Woodgate's group would be responsible for the maintenance and repair of this instrument. A description of this instrument is attached as an Appendix. Note that this instrument requires a lot of setup and calibration; it will be a challenge to get this working remotely. Telescope scheduling will now include nautical twilight as well (earlier, only the time between astronomical twilights has been formally scheduled). Gillespie: Astronomers actually are using the telescope basically from sundown to sunrise, using bright twilight for calibrations, etc. Should we formally schedule this as well? We'll simply state explicitly that the beginning of the night observer has the time from sunset to 12 degree twilight, and equivalently, the end-of-the-night observer shall have the time from 12 degree twilight to sunrise, unless there is a compelling operational or engineering reason that the site staff will need this time. We need to update our master list of publications based on APO observations. If you have not done so already, send full reference and abstract of your papers by e-mail to Rene Walterbos (rwalterb@nmsu.edu). Next meeting will be a face-to-face meeting of the User's Committee at APO on September 29. Previous month's minutes are approved. ************************************************************************ Appendix: A description of Woodgate's Fabry-Perot The Goddard Fabry-Perot/CCD imager has been in active use for 8.5 years at major observatories: KPNO (4m, 2.lm, 0.9m), Steward Observatory (2.2m, 1.5m), MacDonald Observatory (2.7m), the MDM Observatory (1.3m, 2.5m) and the European Southern Observatory (3.6m). Our etalons have been used in other Fabry-Perot instruments at CTIO and CFHT. Observations have been performed by our own core team, and by collaborating with other scientists. We plan to continue these efforts, maintain these capabilities, and to extend them in wavelength range, field of view and spectral resolving power. The current instrument has a choice of 4 Queensgate 50mm diameter piezoelectrically driven, capacitance stabilized etalons which can be tuned to any wavelength in the range 4000-10000A, and with resolution from 4A to 28A FWHM depending on etalon and wavelength. The system throughput including the CCD is 20% in the red and 5% in the blue. The instrument is used at the cassegrain or Nasmyth focus of the telescope. Behind the telescope focus a field lens and collimator lens collimate the light through the etalon and an order-sorting blocking filter, and a camera lens refocuses onto the CCD. We have replaced the 512x512 CCD with a STIS technology SITe 2048x2048 CCD. It has 21 micron pixels, 5 electron rms readout noise, MPP (inverted operation), minichannels, and a very high efficiency down to 3400A (QE is 82% at 4000A, 90% at 7000A and 53% at 9000A). This provides a larger field of view, lower noise, smoother bias levels, higher charge transfer efficiency, and higher sensitivity with UV, visible and IR etalons. We are obtaining a UV etalon covering 3400-4000A, with UV lenses and blocking filters, to cover lower redshifts in Lyman-( and CIV 1550A and [OII] for more complete evolutionary studies as a function of redshift, and to provide access to local [OII] and [NeV] to investigate very extended regions and hot regions of nearby objects. The above etalons have bandwidths of several hundred km/s in order to encompass the velocity distributions within entire galaxies, uncertainties in redshifts, and breadth of absorption line systems for maximum detectability, and for velocity mapping of fast supernova remnants and galaxy clusters. (We hope to obtain a higher resolution etalon, 1-2A FWHM, for velocity studies within galaxies, the interstellar medium, slow supernova remnants, planetary nebulae, circumstellar gas, comets and planetary atmospheres - note this etalon has not yet been purchased.) The field of view at the APO 3.5-meter is 3.3 arcmin with 0.18 arcsec pixels, with a parabolic wavelength gradient. APO APO APO APO APO Apache Point Observatory 3.5m APO APO APO APO APO This is message 374 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