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Proceedings Paper

Rapid refocusing system for the Euro50 telescope aimed at removing the perspective elongation of laser beacons
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Paper Abstract

To obtain full sky coverage, astronomical adaptive optics systems require Na Sodium Beacons (SBs) (also referred to as Laser Guide Stars or LGSs) located at heights extending from 85 to 100 km. When viewed at the edge of large telescopes these SBs appear elongated. For the Euro50 50 meter aperture telescopes this elongation amounts to 6 to 9 arcseconds when the laser is launched from a point on the telescope axis. This is substantially larger than the ~0.6 arcsec FWHM SB when viewed near the telescope center. This so-called "perspective elongation" substantially decreases the sensitivity of SB aided adaptive optics. We describe a way of removing this elongation when using pulsed lasers. It uses rapid (microsecond) refocusing of the telescope with the aid of birefringent lenses and polarization modulators. We present an outline of the SB wavefront sensor for the Euro50.

Paper Details

Date Published: 24 December 2003
PDF: 14 pages
Proc. SPIE 5169, Astronomical Adaptive Optics Systems and Applications, (24 December 2003); doi: 10.1117/12.504238
Show Author Affiliations
Jacques M. Beckers, Univ. of Chicago (United States)
Lund Observatory (Sweden)
Mette Owner-Petersen, Lund Observatory (Sweden)
Torben Andersen, Lund Observatory (Sweden)

Published in SPIE Proceedings Vol. 5169:
Astronomical Adaptive Optics Systems and Applications
Robert K. Tyson; Michael Lloyd-Hart, Editor(s)

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