Primary mirror system for the first Magellan telescope

Hubert M. Martin; R. G. Allen; Brian Cuerden; Scott T. DeRigne; Lee R. Dettmann; Dean A. Ketelsen; Stephen M. Miller III; Giancarlo Parodi; S. Warner

doi:10.1117/12.391497

20 July 2000 Primary mirror system for the first Magellan telescope

Hubert M. Martin, R. G. Allen, Brian Cuerden, Scott T. DeRigne, Lee R. Dettmann, Dean A. Ketelsen, Stephen M. Miller III, Giancarlo Parodi, S. Warner

Author Affiliations +

Proceedings Volume 4003, Optical Design, Materials, Fabrication, and Maintenance; (2000) https://doi.org/10.1117/12.391497
Event: Astronomical Telescopes and Instrumentation, 2000, Munich, Germany

Abstract

We describe the optical fabrication and the active support system of the 6.5 m f/1.25 primary mirror for the first Magellan telescope. 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 small passive tools. The figure was measured with IR and visible interferometers, using refractive null lenses to compensate 810 microns of aspheric departure. After subtraction of Seidel astigmatism and spherical aberration, the finished mirror is accurate to 14 nm rms surface and has an encircled energy of 80% in 0.06' diameter at 500 nm. The mirror was integrated with its active support system in the laboratory, and support forces were adjusted to optimize the figure. The optimization was performed by singular value decomposition of the influence functions into normal bending modes. Using the first 20 modes and a maximum correction force of 46 N, the surface accuracy is 24 nm rms with 80% of the light in 0.11' diameter.

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Hubert M. Martin, R. G. Allen, Brian Cuerden, Scott T. DeRigne, Lee R. Dettmann, Dean A. Ketelsen, Stephen M. Miller III, Giancarlo Parodi, and S. Warner "Primary mirror system for the first Magellan telescope", Proc. SPIE 4003, Optical Design, Materials, Fabrication, and Maintenance, (20 July 2000); https://doi.org/10.1117/12.391497

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