The ADC for the VST Telescope: theory and preliminary test of the electromechanical system
Date Issued
2010
Author(s)
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Ferragina, Luigi
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Abstract
The VST telescope is equipped with an Atmospheric Dispersion Corrector to counterbalance the spectral dispersion introduced by the atmosphere. The well known effect of atmospheric refraction is the bending of incoming light due to variable atmospheric density along the light path. This effect depends on the tangent of the zenith angle and also varies with altitude, humidity and wavelength. Since the magnitude of refraction depends on the wavelength, the resulting effect is not only a deviation of the light beam from its original direction but also a spectral dispersion of the beam. This effect can be corrected by introducing a dispersing element in the instrument. In the VST case the device that compensates for this effect is based on a set of four prisms in two cemented doublet pairs. The system provides an adjustable counter dispersion by counter-rotating the two pairs of prisms. The counter-rotating angle depends on the atmospheric dispersion, which is computed with an atmospheric model using both environmental data (temperature, pressure, humidity) and the telescope position. Two different approaches have been compared for the computations to cross-check the results. The electromechanical system has been assembled, tested and debugged prior to the shipping to Chile. This paper describes the atmospheric models used in the VST case and the most recent phases of work.
Coverage
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation
All editors
Atad-Ettedgui, Eli; Lemke, Dietrich
Series
Start page
773948--
Conferenece
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation
Conferenece place
San Diego, California, United States
Conferenece date
27 June - 2 July, 2010
Issn Identifier
0277-786X
Ads BibCode
2010SPIE.7739E..48S
Rights
open.access
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