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Proceedings Paper

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

Paper Details

Date Published: 8 August 2016
PDF: 12 pages
Proc. SPIE 9906, Ground-based and Airborne Telescopes VI, 99063H (8 August 2016); doi: 10.1117/12.2234468
Show Author Affiliations
Will Saunders, Australian Astronomical Observatory (Australia)
Peter Gillingham, Australian Astronomical Observatory (Australia)
Sean Lin, GMTO Corp. (United States)
Bob Woodruff, GMTO Corp. (United States)
Andrew Rakich, GMTO Corp. (United States)

Published in SPIE Proceedings Vol. 9906:
Ground-based and Airborne Telescopes VI
Helen J. Hall; Roberto Gilmozzi; Heather K. Marshall, Editor(s)

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