Subject: Minutes of APO User's Committee,8/30/99

From: strauss@astro.Princeton.EDU

Submitted: Thu, 2 Sep 1999 13:04:25 -0400 (EDT)

Message number: 374 (previous: 373, next: 375 up: Index)

  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. 

Hiring of Observing Specialists
3.5m Shutdown status 
Woodgate's Fabry-Perot instrument

******************Hiring of Observing Specialists**********************
  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. 


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

  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

  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.

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