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Imaging polarimetry

During October 1991 a mode tried out briefly in February was commissioned (Charles Jenkins and Robert Laing, to whom we refer you for results and recommendations). In this mode, the grating is replaced by a flat mirror (`test flat'), so that a white image is recorded rather than a spectrum; the spectral range is restricted by a (post-slit) filter. The slit is opened to the full width of the calcite plate and a comb Dekker is used to create dark zones for the second image produced by the calcite plate. The polarimetric procedure is identical to that for spectropolarimetry; the only difference is that in this case both dimensions on the detector are spatial. The comb Dekker transmits only part of the image, so several complete observations are needed to fill the image plane.

The main purpose of this mode is to provide additional support to long-slit spectropolarimetry of extended objects; it is not necessarily an optimised polarization imager (the Durham polarimeter is in several aspects, and TAURUS may be when its time comes). For the time being, ISIS is the operationally most accessible imaging polarimeter; imaging and spectropolarimetry can be interleaved with any other ISIS observing programme. Do enquire for up-to-date status.

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Tue Oct 7 17:34:45 BST 1997