AN IMAGING POLARIMETER (IMPOL) FOR MULTIWAVELENGTH OBSERVATIONS

Taking advantage of the advances in array detector technology, an imag ing polarimeter (IMPOL) has been constructed for measuring linear pola rization in the wavelength band from 400 - 800 nm. It makes use of a W ollaston prism as the analyzer to measure simultaneously the two ortho gonal polarization components that define a Stoke's parameter. An achr omatic half-wave plate is used to rotate the plane of polarization wit h respect to the axis of the analyzer so that the second Stoke's param eter also can be determined. With a field of view corresponding to abo ut 30 x 30 mm(2) for a empty set 1.2 m, f/13 telescope, a sensitive, l iquid-N-2 cooled CCD camera as the detector and a built-in acquisition and guidance unit, the instrument can be used for studying stellar fi elds or extended objects with an angular resolution of similar to 2 '' . The instrumental polarization is less than 0.05% and the accuracies of measurement are primarily limited by photon noise for typical obser vations.