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Testing process for the WEAVE prime focus corrector lenses for the William Herschel Telescope
Author(s): Dijana Bogunovic; Graeme Jonas ; Dave Cochrane; Andrew Rakich; Peter Connor; Abe Romeril; Jimi Romeril; Luke Gers; Eleanor Howick ; Chris Young; Tony Reed; Ian Tosh; Émilie Lhomé; Kevin M. Dee; Gavin Dalton ; Scott Trager; Jose Alfonso Lopez Aguerri ; Piercarlo Bonifacio ; Antonella Vallenari ; Esperanza Carrasco ; Don Carlos Abrams; Kevin Middleton
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Paper Abstract

A new prime focus corrector for the WEAVE project for the William Herschel Telescope is being produced. The corrector consists of six lens elements, the largest being 1.1 m in diameter. It also incorporates an Atmospheric Dispersion Corrector. Testing procedures for the WEAVE prime focus corrector lens elements are described here. Critical issues encountered in practice, including the influence of the lens size, wedge and weight on the testing procedure are discussed. Due to large lens dimensions, a dedicated test tower and lens support system has been developed to measure the optical surface form errors of the concave surfaces and the transmitted wavefront of each lens. For some of the lens elements, sub-aperture measurements have been performed using an off-axis Hindle sphere and the resultant OPD maps have been stitched together. The challenge of testing a wedged lens with a combination of a long radius convex surface and a short radius concave surface has been resolved by using another lens from the system as an auxiliary lens. The practice of testing convex surfaces via internal reflection/transmission through the lens element has been avoided entirely in this case and some discussion justifying the choices of metrology approach taken is given. The fabrication and acceptance testing of the lens elements has been completed within the expected time and budget, and all elements have been shown to meet requirements.

Paper Details

Date Published: 6 July 2018
PDF: 6 pages
Proc. SPIE 10700, Ground-based and Airborne Telescopes VII, 107003A (6 July 2018); doi: 10.1117/12.2312342
Show Author Affiliations
Dijana Bogunovic, Callaghan Innovation (New Zealand)
Graeme Jonas , Callaghan Innovation (New Zealand)
Dave Cochrane, Callaghan Innovation (New Zealand)
Andrew Rakich, Mersenne Optical Consulting Ltd. (United States)
Peter Connor, Callaghan Innovation (New Zealand)
Abe Romeril, Callaghan Innovation (New Zealand)
Jimi Romeril, Callaghan Innovation (New Zealand)
Luke Gers, Callaghan Innovation (New Zealand)
Eleanor Howick , Callaghan Innovation (New Zealand)
Chris Young, Callaghan Innovation (New Zealand)
Tony Reed, Callaghan Innovation (New Zealand)
Ian Tosh, STFC Rutherford Appleton Lab. (United Kingdom)
Émilie Lhomé, Isaac Newton Group of Telescopes (Spain)
Kevin M. Dee, Isaac Newton Group of Telescopes (Spain)
Gavin Dalton , STFC Rutherford Appleton Lab. (United Kingdom)
Univ. of Oxford (United Kingdom)
Scott Trager, Univ. of Groningen (Netherlands)
Jose Alfonso Lopez Aguerri , Instituto de Astrofísica de Canarias (Spain)
Piercarlo Bonifacio , GEPI, Observatoire de Paris, CNRS, PSL Research Univ. (France)
Antonella Vallenari , INAF - Osservatorio Astronomico di Padova (Italy)
Esperanza Carrasco , INAOE (Mexico)
Don Carlos Abrams, Isaac Newton Group of Telescopes (Spain)
Kevin Middleton , STFC Rutherford Appleton Lab. (United Kingdom)

Published in SPIE Proceedings Vol. 10700:
Ground-based and Airborne Telescopes VII
Heather K. Marshall; Jason Spyromilio; Roberto Gilmozzi, Editor(s)

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