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

Enrico Giro; Carlotta Bonoli; Franco Leone; Emilio Molinari; Claudio Pernechele; Andrea Zacchei

doi:10.1117/12.458607

14 February 2003 Polarization properties at the Nasmyth: focus of the alt-azimuth TNG telescope

Enrico Giro, Carlotta Bonoli, Franco Leone, Emilio Molinari, Claudio Pernechele, Andrea Zacchei

Proceedings Volume 4843, Polarimetry in Astronomy; (2003) https://doi.org/10.1117/12.458607
Event: Astronomical Telescopes and Instrumentation, 2002, Waikoloa, Hawai'i, United States

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.

Citation Download Citation

Enrico Giro, Carlotta Bonoli, Franco Leone, Emilio Molinari, Claudio Pernechele, and Andrea Zacchei "Polarization properties at the Nasmyth: focus of the alt-azimuth TNG telescope", Proc. SPIE 4843, Polarimetry in Astronomy, (14 February 2003); https://doi.org/10.1117/12.458607

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