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Astron. Astrophys. Suppl. Ser.
Volume 128, Number 2, March I 1998
Page(s) 369 - 375
DOI: 10.1051/aas:1998148

A&A Supplement series, Vol. 128, Mars I 1998, 369-375

Received January 20; accepted July 11, 1997

An imaging polarimeter (IMPOL) for multi-wavelength observations

A.N. Ramaprakashtex2html_wrap537 - R. Guptatex2html_wrap537 - A.K. Sentex2html_wrap541 - S.N. Tandontex2html_wrap537

Send offprint request: A.N. Ramaprakash
tex2html_wrap537 Inter-University Centre for Astronomy and Astrophysics, Post Bag 4, Ganeshkhind, Pune - 411 007, India
tex2html_wrap541 Department of Physics, Assam University, Silchar - 788 001, India


Taking advantage of the advances in array detector technology, an imaging polarimeter (IMPOL) has been constructed for measuring linear polarization in the wavelength band from 400-800 nm. It makes use of a Wollaston prism as the analyzer to measure simultaneously the two orthogonal polarization components that define a Stoke's parameter. An achromatic half-wave plate is used to rotate the plane of polarization with respect to the axis of the analyzer so that the second Stoke's parameter also can be determined. With a field of view corresponding to about tex2html_wrap_inline503 for a tex2html_wrap545 /20D 1.2 m, f/13 telescope, a sensitive, liquid-tex2html_wrap_inline521 cooled CCD camera as the detector and a built-in acquisition and guidance unit, the instrument can be used for studying stellar fields or extended objects with an angular resolution of tex2html_wrap_inline523. The instrumental polarization is less than 0.05% and the accuracies of measurement are primarily limited by photon noise for typical observations.

keywords: instrumentation: polarimeters -- techniques: polarimetry -- polarization

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