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Characterizing Instrumental Effects on Polarization at a Nasmyth focus using NaCo

de Boer, Joshua and Girard, Julien H. and Mawet, Dimitri and Snik, Frans and Keller, Christoph U. and Milli, Julien (2014) Characterizing Instrumental Effects on Polarization at a Nasmyth focus using NaCo. In: Ground-based and Airborne Instrumentation for Astronomy V. Proceedings of SPIE. No.9147. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 914787. ISBN 9780819496157.

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We propose a new calibration scheme to determine the instrumental polarization (IP) and crosstalk induced by either the telescope or an instrument at Nasmyth focus. We measure the polarized blue sky at zenith with VLT/UT4/NaCo for different NaCo derotator and telescope azimuth angles. Taking multiple measurements after rotating both the instrument and the telescope with angles of 90° allows use to determine the IP and most crosstalk components separately for the telescope and the instrument. This separation of the Mueller matrices of UT4 and the NaCo is especially important for measurements taken in the conventional polarimetric mode (field stabilized), because the rotation of the instrument with respect to M3 causes a variation in the IP and crosstalk throughout the measurement. The technique allows us to determine the IP with an accuracy of 0.4%, and constrain or determine lower or upper limits for most crosstalk components. Most notably, the UT4 U → V crosstalk is substantially larger than theory predicts. An angular offset in NaCo's half wave plate orientation is a possible source of systematic errors. We measure this offset to be 1.8° ± 0.5°.

Item Type:Book Section
Related URLs:
URLURL TypeDescription DOIArticle
Girard, Julien H.0000-0001-8627-0404
Mawet, Dimitri0000-0002-8895-4735
Milli, Julien0000-0001-9325-2511
Additional Information:© 2014 Society of Photo-Optical Instrumentation Engineers (SPIE). Paper Date Published: 28 July 2014. JdB acknowledges ESO for its support provided with the studentship program. We furthermore thank ESO staff of the Paranal Observatory for their support during the observations, especially Fernando Salgado.
Subject Keywords:instrumental polarization, crosstalk, calibration scheme, polarimetric differential imaging, high contrast imaging, NAOS-COKICA, SPHERE/ZIJVIPOL, SPHERE/IRDIS
Series Name:Proceedings of SPIE
Issue or Number:9147
Record Number:CaltechAUTHORS:20150521-121335028
Persistent URL:
Official Citation:Jozua de Boer ; Julien H. Girard ; Dimitri Mawet ; Frans Snik ; Christoph U. Keller, et al. " Characterizing instrumental effects on polarization at a Nasmyth focus using NaCo ", Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 914787 (July 28, 2014); doi:10.1117/12.2054970;
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:57740
Deposited By: Ruth Sustaita
Deposited On:21 May 2015 19:52
Last Modified:10 Nov 2021 21:54

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