Fabrication and measured quality of the MMT primary mirror

H. M. Martin, R. G. Allen, J. R.P. Angel, J. H. Burge, W. B. Davison, S. T. DeRigne, L. R. Dettmann, D. A. Ketelsen, W. C. Kittrell, S. M. Miller, P. A. Strittmatter, S. C. West

Research output: Contribution to journalConference articlepeer-review

15 Scopus citations


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 results 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.

Original languageEnglish (US)
Pages (from-to)194-204
Number of pages11
JournalProceedings of SPIE - The International Society for Optical Engineering
StatePublished - 1998
EventAdvanced Technology Optical/IR Telescopes VI - Kona, HI, United States
Duration: Mar 23 1998Mar 25 1998


  • Aspheres
  • Optical fabrication
  • Optical testing
  • Telescopes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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