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The WIYN Report: Progress on the New 3.5-m Telescope (1Jun93) (from KPNO, NOAO Newsletter No. 34, 1 June 1993) The WIYN enclosure was "substantially complete" in mid-March. The contractor is currently working on a final punch list of items to be corrected. In the meantime, KPNO personnel have installed and grouted the lower sole plate for the telescope. The upper sole plates are in position and will be grouted after installation of the telescope fork assembly. The telescope mount has been fully assembled at L&F Industries' plant in Los Angeles. During March shop tests it was discovered that the pillow blocks supporting the elevation axle were slightly misaligned. The instrument rotators were also found to exhibit excessive friction at low rotation rates. L&F is correcting these problems and hopes to disassemble the mount at the end of April in preparation for final painting and shipment to Kitt Peak. The mount will be installed in the WIYN Observatory this spring, hopefully prior to summer shutdown of the other KPNO telescopes. Polishing of the 3.5-m primary mirror at the Steward Observatory Mirror Lab was completed in March. The work was a joint effort involving SOML and NOAO personnel. The final figure achieved over the clear aperture is superb: 22.9 nm RMS and 310.8 nm peak-to-valley. The largest remaining aberration is astigmatism. With the astigmatism term removed, the final figure achieved is 15.7 nm RMS and 188 nm peak-to-valley. The mirror and cell have been returned to NOAO, and work is in progress converting the cell for installation in the telescope. New axial mirror supports have been designed, prototyped and tested. Sixty-six of the units (plus spares) are currently being fabricated. The supports will be able to apply controllable forces to warp the mirror and correct for slowly varying changes in the figure, such as astigmatism. The intent is to correct the residual, low-order polishing errors, thermal distortions and force errors in the supports themselves using an image analyzer to provide the necessary feedback from the focal plane. The primary mirror lateral supports are also under review for possible modifications at the same time the rest of the cell and thermal controls are being made ready for installation in the telescope. Work on the mirror support and thermal system controls is proceeding in parallel with the mechanical effort. The secondary mirror is being polished by Contraves in their Pittsburgh facility. This effort is underway and is expected to produce a finished mirror in October 1993. The tertiary mirror is being polished by Kodak in a two step process. Grinding and initial polishing to about 1 wave peak-to-valley were performed on a large planetary polishing machine. This completed, the optic is scheduled to go into Kodak's ion polishing machine for final figuring. Work continues on controls and instrumentation for the WIYN Observatory. The University of Wisconsin is fabricating the control system and expects to begin installation this summer. At NOAO, engineering and design of the modifications necessary to move the Multi-Object Spectrograph and Hydra fiber-optic positioner from the 4-m telescope to WIYN are underway. The design of the CCD Imager and filter wheel assembly is progressing at Indiana. Matt Johns, Caty Pilachowski
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