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Proceedings Paper

Improved telescope focus using only two focus images
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Paper Abstract

In an effort to reduce the amount of time spent focusing the telescope and to improve the quality of the focus, a new procedure has been investigated and implemented at the Canada-France-Hawaii Telescope (CFHT). The new procedure is based on a paper by Tokovinin and Heathcote and requires only two out-of-focus images to determine the best focus for the telescope. Using only two images provides a great time savings over the five or more images required for a standard through-focus sequence. In addition, it has been found that this method is significantly less sensitive to seeing variations than the traditional through-focus procedure, so the quality of the resulting focus is better. Finally, the new procedure relies on a second moment calculation and so is computationally easier and more robust than methods using a FWHM calculation. The new method has been implemented for WIRCam for the past 18 months, for MegaPrime for the past year, and has recently been implemented for ESPaDOnS.

Paper Details

Date Published: 23 July 2008
PDF: 8 pages
Proc. SPIE 7018, Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation, 70183V (23 July 2008); doi: 10.1117/12.787649
Show Author Affiliations
Gregory Barrick, Canada-France-Hawaii Telescope (United States)
Tom Vermeulen, Canada-France-Hawaii Telescope (United States)
James Thomas, Canada-France-Hawaii Telescope (United States)

Published in SPIE Proceedings Vol. 7018:
Advanced Optical and Mechanical Technologies in Telescopes and Instrumentation
Eli Atad-Ettedgui; Dietrich Lemke, Editor(s)

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