Subject: 3.5m shutdown further extended

From: elt@astro.Princeton.EDU

Submitted: Wed, 8 Jan 1997 16:27:22 -0500 (EST)

Message number: 114 (previous: 113, next: 115 up: Index)

		APO 3.5M SHUTDOWN FURTHER EXTENDED

Unfortunately, it is now necessary to extend the shutdown of the 3.5m
by an indefinite number of days.  Science operations should be considered
canceled until you are notified otherwise.  Said notification will be
issued at least 24 hours in advance, through both general electronic
broadcast channels and email directed to the most immediately affected
PIs and observers.  This message is also being distributed in this
manner.  Schedulers, please do your best to bring these messages to
the attention of your affected colleagues.

The primary reason for this extension is delays caused by severe winter
weather at APO.  Heavy snowfall has made access to the observatory
difficult and time consuming, though staff members have managed to reach
the site each day.  More seriously, extremely cold temperatures in
the enclosure, ranging from single digits to the 20's, have greatly
slowed progress on re-assembly of the telescope optics.  There is
extensive frosting within the enclosure, including exposed optical
surfaces (but not the primary).  Moreover, safe handling of delicate
optical and mechanical components in such difficult working conditions
requires going slowly and carefully.  Furthermore, once re-assembly of
the telescope is accomplished, approximately 1.5 clear nights on the
sky are needed to re-establish alignment, a pointing model, focus
settings, instrument blocks and so forth.  If photometric conditions
prevailed during this period, it would also be very desirable to make
some initial post re-aluminization throughput measurements.  Unhappily,
though the recent storm has moved east, another front is expected at
the end of the week with more snow and severe weather forecast for
the weekend.

Thus, it appears likely that the telescope cannot be available for
science use until sometime next week, or possibly longer if there
is a siege of bad weather.  [Of course, science observations would
be impossible anyway during such weather, so the time lost to the
shutdown is inflated somewhat artificially.  Baring unhappy surprises,
the *useful* time lost to this extension will be only 1 to 2 nights,
even if a much longer period of calendar time elapses.]  In
these circumstances, it appears more reasonable to extend the
shutdown until further notice than to continue to do it in small
increments of one or two nights.

Ed Turner
APO APO APO APO APO  Apache Point Observatory 3.5m  APO APO APO
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