25 August 1998 VLT beryllium secondary mirror no. 1: performance review
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Abstract
The four Very Large Telescope secondary mirrors are 1.2-m Beryllium lightweight convex mirrors. REOSC has been selected for the design and manufacturing of the optics and of their supporting system. The first mirror unit has been delivered in September, 1997. Operating from visible to near infrared, the mirror defines the telescope aperture stop and may be chopped during observation. The optical requirements are tight and a high stiffness, low weight and inertia are requested as well. Using beryllium is a technical challenge for such a large optic manufacturing, in particular regarding its stability. The requirements and design are presented, we review the mirror manufacturing steps: blank production, machining, grinding, Nickel plating, polishing, integration and testing. The optical quality control method, a problem for large convex mirrors control, is detailed. The results of acceptance testing of mirror No. 1 are summarized, we present conclusions about the mirror figure stability. The status of the three additional mirrors manufacturing is presented to conclude.
© (1998) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Marc Cayrel, "VLT beryllium secondary mirror no. 1: performance review", Proc. SPIE 3352, Advanced Technology Optical/IR Telescopes VI, (25 August 1998); doi: 10.1117/12.319281; https://doi.org/10.1117/12.319281
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