1 June 1994 Two-channel optical imaging polarimeter
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Abstract
The complexity of the structure of many astronomical objects (viz. galaxies, nebulae, comets etc.) is such that details of polarization frequently requires seeing limited resolution. A two channel imaging polarimeter has been described here which can provide seeing limited spatial resolution and highly accurate values of linear polarization by minimizing the harmful effects of atmospheric variations. This can be achieved by using a Wollaston prism analyzer to split a telescope image into two polarized components and simultaneously comparing them to eliminate effect due to atmospheric scintillation. The introduction of a grid at the focal plane, prevents the overlapping of o and e images on the CCD plane, where the image is refocussed. In order to keep the orientation of the two polarized components fixed in the instrument frame, the polarization vector of the image is modulated by mechanically rotating a half wave plate and readings are taken for several positions of the half wave plate to derive the polarization vector. We plan to use the above instrument at the cassegrain plane of 2.3 m V B telescope, India (f/13 beam) to carry out imaging polarimetry of extended astronomical objects. With 1000 secs. exposure time for each frame, on the GEC/EEF P8603A CCD chip, one can measure polarization values with an uncertainty of 0.3%, for the Seyfert N1068 (mv equals 17.5 per square arc sec) when observed in V band. This uncertainty is mainly dominated by photon count statistics. This instrument is presently being fabricated at Inter University Center for Astronomy and Astrophysics, Pune, India.
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Asoke K. Sen, Asoke K. Sen, S. N. Tandon, S. N. Tandon, } "Two-channel optical imaging polarimeter", Proc. SPIE 2198, Instrumentation in Astronomy VIII, (1 June 1994); doi: 10.1117/12.176703; https://doi.org/10.1117/12.176703
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