Subject: APO 3.5m User's Committee meeting minutes, 10/14/02

From: strauss@astro.Princeton.EDU

Submitted: Fri, 18 Oct 2002 22:42:53 -0400 (EDT)

Message number: 625 (previous: 624, next: 626 up: Index)

  Apache Point Observatory 3.5m User's Committee Meeting
		October 14, 2002

Attending: Al Harper, Bruce Gillespie, Ed Turner, Michael Strauss,
Rene Walterbos, Bruce Balick, Mike Shull

Absent: Alan Uomoto, Don York, John Morse, Chris Stubbs, Jon Holtzman

Testing the telescope collimation
Washing the primary mirror
Miscellaneous hardware news
User/Site Interface issues

************Testing the telescope collimation**********************

As reported last month, APO has started a program of monitoring the
collimation of the telescope roughly twice a week using a
Shack-Hartmann test.  First results are summarized on the following web

  It appears that the collimation seems steady for a while, then
suddenly jumps.  The collimation appears to move much more frequently
in one axis than the other.  More data are definitely needed to find
out what is going on.  There is broad support from the user's
committee to continue this effort; it has the potential to greatly
improve image quality.

  Some discussion of whether we know that it is the top end that is
causing the trouble.  It is a logical possibility that the problem
might be somewhere else, such as with the primary mirror support or
the tertiary.  Needless to say, we would like to know this; this
information could inform the decision whether to build a new top end. 

*****************Washing the primary mirror************************

As was reported recently (apo35-general #620), a freak rain shower
caught the observers unawares, and rain fell on the primary mirror.
It left rain spots, which should be cleaned off; see the images at:

To wash the mirror requires removing it from its cell, which is a
several-day operation.  The current plan is to carry this out starting
Monday, October 21 (which is scheduled engineering time); it would
take roughly 5 nights.  This may be postponed if it is too cold; one
doesn't want the washing water to freeze. 

Holtzman has shown that this has not affected the throughput much, but
it may be producing scattered light. It also will chemically degrade
the aluminum over time, to the point that permanent coating damage
will be likely if the spots are not removed quickly.

  So how did we get rained on in the first place?  It's impossible to
keep rain off a mirror unless you never open the telescope.  There are
situations where rain will fall out of a perfectly clear sky, the rain
being blown horizontally many tens of miles before hitting the ground.

To get a sense of the trade-off, our estimates are that closing the
telescope an extra 4 nights per month (!!) on average would reduce the
rate of wetting the mirror from approximately once per year to once
per decade

  One possibility that was discussed was to use a series of radio rain 
detectors on the site; these could give a few minute warning.  If rain
is detected, the immediate thing to do is to close the mirror covers,
then go to the dome to close the shutter. 

********Miscellaneous: Cloud camera, Baffling, Instrument Status**************

  Speaking of weather, the IR cloud-monitoring camera has been
upgraded to a much more sensitive system, which can make a continuous
movie of cloud cover (the old system gave an image every five
minutes).  Jim Gunn, Doug Finkbeiner, Dave Schlegel and others are the
ones who have made this happen. Check out (link off the APO home page)
for the latest image, and example recent movies.  Note that unlike the
previous camera, white refers to clouds; a cloudless night appears
  But this system is still in a rudimentary form, and needs proper

  A design now exists for the telescope baffling, thanks to Jeff
Morgan.  There will be a design review in early November.  The plan is
to start fabrication next month; it will take about 1.5 months to
build.  Installation may straightforward (i.e., it might be done during
the day); the first component may be in as early as January and
February.  This will be the first of two baffles that that need to be
put into place.

  Most of the relevant instrument pundits were not available for the
meeting, but briefly:
  Mike Carr plans to do a mechanics tune-up on DIS in mid-November.
The DIS optics will be upgraded in December, to better match the new
  The new Echelle acquisition camera/guider is in hand, and will be
installed in November. 

*****************User/Site interface Issues************************************

  We've had a number of problems lately with interfaces between
observatory and users.  Most of these are of the nature of astronomers
not quite understanding that the observatory does not have the
resources to do all the handholding that one might be used to at a
national observatory.  In particular, there have been a number of
examples of:

  -People showing up late for their observing run.  See apo35-general
618.  People have been known to show up right at twilight, and to use
precious dark sky time for flat-fields that they could have done just
as well just after sunset.  There is a policy in place for what to do
if an observer doesn't show up at all, and if someone is late, it
leaves the observing specialist in quite a bind whether to switch to
backup projects, engineering projects etc. 

  -Some novice observers are showing up on site without any person to
teach them the ropes.  While the mountaintop staff will provide
orientation for new observers who are familiar with observing in
general, but the training of novice observers without substantial
experience on any telescope is the responsibility of the individual
institutions (in the form, e.g., of a thesis advisor coming along on
the run).  (Editor's note: this policy needs to be formalized; more to
follow in future postings). 

  -Telescope time allocation forms have been filled out
incorrectly/unclearly (apo35-general 611).  One common occurence is
that an observer requests, say, 6 half-nights.  Their local TAC cuts
them back to 3 half-nights.  Ed Turner is then left with a dilemma
when he tries to schedule these 3 half-nights, and the instructions
make reference to 'three sets of two adjacent half nights, separated
by four nights'.  It may be appropriate to have people rewrite
telescope allocation requests, after they see how much time they've
actually been allocated.  

  -Non-standard filters:
    There was a recent case of an observer putting in a request for a
non-standard filter into a proposal, and then assuming that that was
sufficient to have it available on the mountain.  The APO policy for
filters is given below in the appendix. 

  At the Seattle AAS meeting in January, we will hold one or more
meetings for the 3.5m community to discuss future plans for the
telescope and other issues.  Details will follow.

 Next meeting:  Monday, November 11, 11:30 AM 

*************Appendix: Recap of Special Filter Policy***************

Loaned and Special filters policy

Filters of the appropriate size may be brought/mailed to APO for use 
in SPIcam and DIS.  Use of astronomer-furnished filters in the other 
instruments is discouraged.  Notify APO staff 
( at least 2 weeks in advance if you intend 
to bring and use standard-size filters in SPIcam or DIS.  We require 
that these filters be at APO at least two working days prior to 
their planned use.  For filters with non-matching shapes or sizes, 
contact at least one month in advance of 
their planned use for an evaluation of feasibility.

Unless there is a compelling reason made in writing to the Director, 
all loaned filters at APO will be made available to other telescope 
users without first securing the owner's permission. A list of the 
loaned filters will be kept on the APO website, with the owner's 
name and contact information.  If an astronomer wishes to use one or 
more of these filters, it would be advisable to contact its owner to 
ensure that the filter(s) will be at APO when needed.

If a loaned filter is damaged or lost while at APO, the observatory 
will assume responsibility for its replacement.  Filters will be 
fully insured by the owner when shipped to the site, and filters 
will be fully insured by APO when they are shipped back to the owner.

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