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Astron. Astrophys. 344, L45-L48 (1999)


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Letter to the Editor

Laser guide star adaptive optics: measuring the sodium column density using a magneto-optical filter

P. Patriarchi 1 and A. Cacciani 2

1 CAISMI-CNR, Largo E. Fermi 5, I-50125 Firenze, Italy
2 Dipartimento di Fisica, Universitá di Roma "La Sapienza", P.le A. Moro 2, I-00185 Roma, Italy

Received 26 October 1998 / Accepted 15 February 1999

Abstract

A general use of the adaptive optics requires an artificial guide star created by focusing a laser beam tuned to the sodium D2 line. We propose here a system to monitor the column density of the mesospheric sodium layer which is based on the sodium magneto-optical filter already widely used in solar observations. The principal characteristics of this system are high transmission and high spectral resolution which allow to perform measurements in minutes on a relatively small (e.g. 50 cm diameter) telescope, where the filter can easily mounted due to its compactness.

Key words: instrumentation: adaptive optics

Send offprint requests to: P. Patriarchi (pat@arcetri.astro.it)

© European Southern Observatory (ESO) 1999

Online publication: March 18, 1999

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