Online control of an active telescope secondary mirror

Daniele Gardiol; Claudio Pernechele

doi:10.1117/12.360056

27 August 1999 Online control of an active telescope secondary mirror

Daniele Gardiol, Claudio Pernechele

Proceedings Volume 3737, Design and Engineering of Optical Systems II; (1999) https://doi.org/10.1117/12.360056
Event: Optical Systems Design and Production, 1999, Berlin, Germany

Abstract

Sometimes during a scientific data acquisition the focus of a telescope may change, especially for medium- and long-time exposures. This is mainly due to temperature changes inducing an expansion of the serrourier truss, and more generally, due to elastic structural flexures. Modelization and control of defocusing effect is an important topic in telescopes with great magnification ratio. In the Telescopio Nazionale Galileo case, a 3.5 meters class telescope located in La Palma island, a temperature change of 1 degree induces a 0.9 arcsec image blue. In such a case a control of defocus during an acquisition is essential to obtain sub-arcsec images, thus exploiting the site seeing. The secondary mirror of Galileo telescope is actively controlled via a hexapod actuator. Both systems, the hexapod secondary support and the control system, have been completed and tested at the telescope. The results show that positioning of the mirror is smooth enough, introducing an image movement of about 0.1 arcesc and allowing in such a way the on-line correction also during scientific operations.

Citation Download Citation

Daniele Gardiol and Claudio Pernechele "Online control of an active telescope secondary mirror", Proc. SPIE 3737, Design and Engineering of Optical Systems II, (27 August 1999); https://doi.org/10.1117/12.360056

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