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Proceedings Paper

Polarization properties at Nasmyth: focus of the alt-azimuth TNG telescope
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Paper Abstract

In alt-azimuth telescopes Nasmyth foci are suitable focal planes to reduce mechanical instrument complexity and costs. However, they present some disadvantages mainly due to the field rotation. This is a particularly crucial point in polarimetric observations. Because of the folding mirror, the radiation polarization state is so modified that, to avoid systematic errors, instrumental polarization has to be removed as a function of the telescope position. A model of the polarization introduced by the Telescopio Nazionale Galileo (TNG) at its focal plane is presented. The model takes into account physical and geometrical properties of the optical system, complex refraction index of the mirrors and their relative position, deriving instrumental polarization as a function of the pointing coordinates of the telescope. This model has been developed by means of Muller matrices calculation. Telescope instrumental polarization has been measured following some standard polarization stars at different telescope positions. The mathematical model, here discussed, was confirmed comparing the theoretical results and the experimental measurements at the TNG instruments.

Paper Details

Date Published: 14 February 2003
PDF: 9 pages
Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); doi: 10.1117/12.458607
Show Author Affiliations
Enrico Giro, INAF (Italy)
Osservatorio Astronomico di Padova (Italy)
Carlotta Bonoli, INAF (Italy)
Osservatorio Astronomico di Padova (Italy)
Franco Leone, INAF (Italy)
Osservatorio Astrofisico di Catania (Italy)
Emilio Molinari, INAF (Italy)
Osservatorio Astronomico di Merate (Italy)
Claudio Pernechele, INAF (Italy)
Osservatorio Astronomico di Padova (Italy)
Andrea Zacchei, INAF (Italy)
Osservatorio Astronomico di Trieste (Italy)

Published in SPIE Proceedings Vol. 4843:
Polarimetry in Astronomy
Silvano Fineschi, Editor(s)

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