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The WIYN Mirror (1Dec92)
(from KPNO, NOAO Newsletter No. 32, 1 December 1992)

This quarter saw the completion of the test program for the active
optics system and the thermal control system of the WIYN 3.5-m primary
mirror.  Scatterplate interferograms were taken with the systems under
test in both vertical and horizontal orientation. A list of system
upgrades has been identified and will be incorporated.

The next phase is the grinding and polishing activity which takes the
current sphere to an f/1.75 asphere. At the beginning of August, the
University of Arizona submitted a proposal to do the grinding and
polishing at the Steward Observatory Mirror Lab.  Because the polishing
facilities were ultimately made available to NOAO starting in
September, the accepted proposal specifies a completion date of 30
April 1993 for the WIYN mirror, and it provides a polished mirror at
least six months ahead of the NOAO in-house polishing schedule.

Contract negotiations and approval required considerable effort to
complete in the allotted time.  We are grateful for the assistance of
the AURA Corporate Office and the NSF in expediting this process, and
to our own Contracts and Administrative Services personnel for their
heroic efforts. The signed contract was delivered on 15 September.
Later that day, the mirror was delivered to Steward Mirror Lab.

Development of the bar lap polishing technique has been halted; the
Steward stressed lap approach will be used instead. The WIYN mirror
will be ground in the Steward polishing cell and then transferred to
the NOAO mirror cell for final polishing. This transfer will allow use
of the NOAO polishing supports and thermal control system for final
polishing.

Larry Daggert, Richard Green

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