An all-silica three element wide-field corrector for GMT

Will Saunders; Peter Gillingham; Sean Lin; Bob Woodruff; Andrew Rakich

doi:10.1117/12.2234468

8 August 2016 An all-silica three element wide-field corrector for GMT

Will Saunders, Peter Gillingham, Sean Lin, Bob Woodruff, Andrew Rakich

Proceedings Volume 9906, Ground-based and Airborne Telescopes VI; 99063H (2016) https://doi.org/10.1117/12.2234468
Event: SPIE Astronomical Telescopes + Instrumentation, 2016, Edinburgh, United Kingdom

Abstract

We present an alternative Corrector-ADC design for GMT. The design consists of just 3 silica lenses, of maximum size 1.51m, and includes only a single low-precision asphere for 20' field-of-view, and none for 10'. The polychromatic (360nm-1300nm) image quality is d₈₀<0.043" at zenith and d₈₀<0.20" for ZD<60 degrees. The monochromatic image quality is d₈₀<0.1" everywhere, and typically ~0.05". The ADC action is achieved by tilt and translation of all three lenses; L1 and L2 via simple slide mechanisms each using a single encoded actuator, and L3 via a novel ‘tracker-ball’ support and three actuators. There is also a small motion of M2 via the hexapod, automatically generated by the AGWS system. The ADC action causes a small non-telecentricity, but this is much less than the unavoidable chromatic effects shared with the baseline design. The ADC action also changes the distortion pattern of the telescope, but this can be used positively, to reduce the maximum image motion due to differential refraction by a factor of three. The transmission is superb at all wavelengths, because of the reduced number of air/glass surfaces, and the use only of fused silica.

Citation Download Citation

Will Saunders, Peter Gillingham, Sean Lin, Bob Woodruff, and Andrew Rakich "An all-silica three element wide-field corrector for GMT", Proc. SPIE 9906, Ground-based and Airborne Telescopes VI, 99063H (8 August 2016); https://doi.org/10.1117/12.2234468

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