Subject: User's Committee Meeting of 2/5/96 Minutes

From: Michael Strauss

Submitted: Tue, 6 Feb 1996 08:11:14 -0500 (EST)

Message number: 46 (previous: 45, next: 47 up: Index)

  Minutes of APO 3.5m User's Committee Phone Conference
		February 5, 1996

  Attending: Alan Uomoto, Bruce Gillespie, Ed Turner, Lew Hobbs,
Michael Strauss, Rene Walterbos, Chris Stubbs, Alan Uomoto, Julie Lutz

  What was done during shutdown
  Action items for future
  Opening up the website
  Trading 3.5m time for WIYN at KPNO

Gillespie: Telescope is definitely back on line following week-long
shutdown; ready for science tonight.

Stubbs: Two objectives for shutdown:
  1. Specific technical goals
  2. Improving communication between APO and UW people

(2) was very successful. (1) less so, because of very poor weather. In
the time they could look at the sky, they found a strong oscillation
(many arc-second!) in the secondary structure when pointing directly
(i.e., within 10 degrees) into the wind. If you are 20 degrees away
from the wind, the problem is much less severe. It remains unclear
exactly what is wiggling with respect to what.
  Action item: Redo the rectangular metal piece which holds the
secondary, to try to minimize this windshake.

  Chasing down scattered light and baffling problems: More can be done
than is has been done so far. Stubbs et al are in the process of
putting together a specific characterization of this. 

Primary mirror support system consists of a set of pneumatic
bellows. The FWHM is a systematic function of zenith angle, indicative
of possible substantial contribution to the seeing disk from the
primary support vibrating, at least at high airmass.

  Gillespie: Kibblewhite et al see a 1 Hz motion from the primary as
well. A possible solution is to copy mirror support system from 2.5m,
but this is a delay of at least a year to get this up and
running. Stubbs and Gillespie are trading ideas on how to do this

  Stubbs: Need to start building up a database of image quality data
with the guider, as a diagnostic.
  Plans to use piezoelectric drivers on the secondary to be able to do
tip-tilt corrections; Stubbs et al are working on implementing this. 

  Attempt to correlate secondary shape with Hartmann test results: are
the problems in the figure due to the secondary? Jon Holtzman (NMSU)
has looked into this; unfortunately, results are unambiguous. We may
indeed have to do a prime focus Hartman test of the primary.

  Guiding across the meridian: the (off-axis) guider image stays put,
but the image on the (on-axis) instrument does not (movements of
10"!). The problem has to be in the rotator, which has to flip by 180
degrees as you go through the meridian. Motor for rotator was replaced
with something stronger first day of shut-down, but it didn't
work. We're back to the old, weaker motor.

Gillespie: Software: Russ Owen and Brian Yanny have updated TCC,
mostly for various aspects of DSC operations.

A global list of tasks for the telescope from Stubbs was circulated
with last month's minutes (apo35-general #43).  Strauss suggested the
following further items:
   1. Calibration of DIS with arc lamps:
     a. The ability to turn on lamps and close mirror cover remotely, without
	having to go out to the dome;
        (In progress; controllable by observing specialist from
	 control room. Remote control of this by software is a more
	 distant goal). 
     b. Elimination of any systematic shifts of arc lines relative to sky lines.
   2. Bringing REMARK, and all telescope software under control of
people at ARC (as opposed to having to rely on Lowenstein and Yanny
for future updates for the long term). Possible updating it to an
X-window environment rather than the present Mac.
   3. The ability to control DSC from remark.
   (These two items are dead in the water for the moment; the ARC
    board did not assign any money for this, given the expense of a
    new secondary. There is money, however, to pay Lowenstein to do 
    further work, especially to bring DSC under remark. Ultimately,
    however, much of the software needs to be regenerated from
    scratch. 1.5 solid years of work for one expert person.) 
   4. Characterization of calibration needs of different instruments
	(for example, what are possible flexure problems in DIS? Given these,
	how often is it necessary to redo arc and flat field calibrations)?
    Jon Brinkmann is working hard on this.   

  Measurement of on-sky exposing efficiency of the observatory to find
out where the bottlenecks are. We need to find ways to measure this.

  No negative response to the idea of opening up the web site to the
public. Gillespie is concerned about having the nightly logs available

  Gillespie (report added after the meeting itself):
Status of Enclosure Wheel Repair:

L&F have been unable to obtain an acceptable proposal from the initially
contacted "riggers" (people that run the cranes, hoists, forklifts, etc.)
on how and when they would remove the first wheel and its truck.  This
rigger's most recent proposal involved cutting hatches in the outside of
the enclosure and removing the wheel from the outside (Don York always
wanted to put more ventilation openings in the telescope enclosure!).  L&F
and we believe that the job can be done from the inside, and have engaged
other vendors to provide us with proposals and quotations of price and
schedule.  The first of these visited APO late last week.

We therefore don't yet have a schedule nor definite plan on the repair of
the first enclosure wheel, and we will continue to operate the telescope as
is has been.

  Walterbos: How about the idea of trading time between WIYN and APO,
given their very complementary instrument complements? 
  Turner: At this stage, introducing a whole new institution or two of
users to APO would be a significant drain on operations. On the long
term, the larger the user community, the more pressure to do a wider
range of things. Ed feels that it makes sense to look into this
sometime in the future when "operations calm down". Also keep in mind
that we can compete for WIYN telescope time through NOAO; we would
lose that if we had some special deal through a trade. The user's
committee should query others at their institutions to see if there is
widespread interest in this. 

  Turner: Recommends that each institution make sure that they have the
facilities that shows how to use remark via the SLIP connection over
the phone.

Next meeting. Monday, March 11, 12 noon. 
APO APO APO APO APO  Apache Point Observatory 3.5m  APO APO APO
APO  This is message 46 in the apo35-general archive. You can find
APO  the archive on
APO  To join/leave the list, send mail to
APO  To post a message, mail it to