A novel quadruple beam imaging polarimeter and its application to Comet Tanaka-Machholz 1992 X
- Cite this article as:
- Geyer, E.H., Jockers, K., Kiselev, N.N. et al. Astrophys Space Sci (1996) 239: 259. doi:10.1007/BF00645780
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For observations of solar system objects an imaging polarimeter has been constructed as an auxiliary instrument for a f/15 focal reducer. With this instrument simultaneous measurement of theQ andU Stokes parameters is possible. It contains no moving parts such as a moving λ/2 retarder. The polarizer consists of two Wollaston prisms which are combined to form a single optical element. Their polarization angles differ by 45°. This compound polarizer is placed in the exit pupil of the afocal telescope-collimator system of the focal reducer and splits the exit pupil into halves. In this way four polarized beams with E-vector orientations 0°, 90°, 45°, and 135° emerge from the exit pupil. These are intercepted by the camera lens of the focal reducer system and imaged simultaneously on the CCD detector. With a properly designed field mask at the Cassegrain focus, the four beams are imaged without overlap.
As a demonstration of the capabilities of this quadruple-beam Wollaston-prism polarimeter, we present observations of comet Tanaka-Machholz 1992 X in May 1992. The advantages, shortcomings, and possible improvements of the instrument are discussed.