LBT primary mirrors: the final design of the supporting system

Giancarlo Parodi; G. C. Cerra; John M. Hill; Warren B. Davison; Piero Salinari

doi:10.1117/12.269057

21 March 1997 LBT primary mirrors: the final design of the supporting system

Giancarlo Parodi, G. C. Cerra, John M. Hill, Warren B. Davison, Piero Salinari

Proceedings Volume 2871, Optical Telescopes of Today and Tomorrow; (1997) https://doi.org/10.1117/12.269057
Event: Optical Telescopes of Today and Tomorrow, 1996, Landskrona/Hven, Sweden

Abstract

The main final results in terms of stresses and optical performances are reported for the large binocular telescope (LBT) primary mirrors. The two borosilicate LBT primary mirrors f/1.14 have 8.4 diameter and are produced at the Steward Observatory Mirror Lab (SOML). They are honeycomb shaped in order to achieve light weight, short thermal constant and high stiffness. The back plate is flat and the upper is paraboloid shaped. Each elementary cell has, in the lower plate, one circular hole permitting the ventilation of cell itself. The material used is the borosilicate Ohara E6. Different supporting systems have been analyzed from the mirror casting to the operative conditions, i.e.: supporting system during the cooling of the casting phase; supporting system for the handling after the casting phase and before the optical surface grinding and polishing; supporting system for the handling after the optical surface polishing and for maintenance; passive support system in non-operative condition; supporting system in operative condition. The stress checks carried out show that the values of the maximum principal tensile stresses are below 0.7 MPa for long times and/or stresses affecting large volumes, and are below 1.05 MPa for short times and small volumes. Optical performances in operative condition respect the specification.

Citation Download Citation

Giancarlo Parodi, G. C. Cerra, John M. Hill, Warren B. Davison, and Piero Salinari "LBT primary mirrors: the final design of the supporting system", Proc. SPIE 2871, Optical Telescopes of Today and Tomorrow, (21 March 1997); https://doi.org/10.1117/12.269057

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