Subject: Minutes from October 27 User's Committee meeting

From: strauss@astro.Princeton.EDU

Submitted: Sat, 1 Nov 1997 14:31:37 -0500 (EST)

Message number: 204 (previous: 203, next: 205 up: Index)

   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

  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
  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

  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

  Corson: The main operational-relevant things that have been improved
    Secondary truss support
    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

  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
  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
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