Fabrication and measured quality of the MMT primary mirror

Hubert M. Martin; R. G. Allen; James Roger P. Angel; James H. Burge; Warren B. Davison; Scott T. DeRigne; Lee R. Dettmann; Dean A. Ketelsen; W. Cary Kittrell; Stephen M. Miller III; Peter A. Strittmatter; Steve C. West

doi:10.1117/12.319255

25 August 1998 Fabrication and measured quality of the MMT primary mirror

Hubert M. Martin, R. G. Allen, James Roger P. Angel, James H. Burge, Warren B. Davison, Scott T. DeRigne, Lee R. Dettmann, Dean A. Ketelsen, W. Cary Kittrell, Stephen M. Miller III, Peter A. Strittmatter, Steve C. West

Author Affiliations +

Proceedings Volume 3352, Advanced Technology Optical/IR Telescopes VI; (1998) https://doi.org/10.1117/12.319255
Event: Astronomical Telescopes and Instrumentation, 1998, Kona, HI, United States

Abstract

The primary mirror for the Multiple Mirror Telescope Conversion is the first 6.5 m honeycomb sandwich mirror cast and polished by the Steward Observatory Mirror Lab. We describe the optical fabrication and testing of the f/1.25 paraboloid, and present the final measurements of figure accuracy and inferred image quality. Figuring was performed with a 1.2 m stressed lap--which bends under active control to match the local curvature of the optical surface--and a variety of small passive tools. The mirror was pressurized to compensate for polishing loads and thereby eliminate print-through of the honeycomb structure. The net result is a smoother surface on scales of 5 - 20 cm than has been achieved on previous honeycomb sandwich mirrors. The figure was measured with IR and visible interferometers, using refractive null correctors to compensate 810 microns of aspheric departure. The final measurements were used to calculate synthetic stellar images in a variety of seeing conditions.

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Hubert M. Martin, R. G. Allen, James Roger P. Angel, James H. Burge, Warren B. Davison, Scott T. DeRigne, Lee R. Dettmann, Dean A. Ketelsen, W. Cary Kittrell, Stephen M. Miller III, Peter A. Strittmatter, and Steve C. West "Fabrication and measured quality of the MMT primary mirror", Proc. SPIE 3352, Advanced Technology Optical/IR Telescopes VI, (25 August 1998); https://doi.org/10.1117/12.319255

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