Paper
27 August 1999 Online control of an active telescope secondary mirror
Daniele Gardiol, Claudio Pernechele
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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.
© (1999) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
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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CITATIONS
Cited by 2 scholarly publications.
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KEYWORDS
Mirrors

Telescopes

Control systems

Active optics

Computer programming

Temperature metrology

Lanthanum

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