A Search for the Regional Variations in the Wavelength Dependence of Interstellar Polarization

Abstract

The Polarization of 19 Bright, Highly Polarized Stars was measured from March until July 1965, with a differential polarimeter installed at the Cassegrain focus of the 90-cm telescope of the Toruń Observatory in Poland. The stellar light was split by the calcite Wollaston prism into two beams falling upon the cathodes of the photomultipliers. The observations were made at eight position angles of the polarimeter differing by 45°, alternately with and without the quartz depolarizer. The yellow 2-mm Schott GG 14 and the blue Schott BG 12 (l-mm) + GG 13 (2-mm) filters were used. No optical elements except the depolarizer were placed between the Wollaston prism and the telescope mirrors.Usually only the Stokes parameters having the larger absolute values were accurately measured. The resulting polarization ratios pv/pB of the Stokes parameters expressed in magnitudes, measured with yellow and blue filters, are given in the ninth column of table I.