Polarization of Comet Arend–Roland

Abstract

WHEN, last May, Comet Arend–Roland became a bright naked-eye object in the northern hemisphere, we carried out a series of photoelectric measures of the polarization of its coma at different phase angles. The technique employed utilized a piece of ‘Polaroid’ attached to a rotatable six-position disk contained in the photometer. This enables measurements of intensity to be made as the ‘Polaroid’ is turned through 60 dog. for each position of the disk. Standard B and V filters employed in the UBV system, together with interference filters having peak transmissions centred on 5890 A., 5000 A., 4700 A. and 4300 A. and half-widths of 80 A. were used for isolating the different wave-lengths. Each of the three circular apertures behind the ‘Polaroid’ transmitted 3.7 square minutes of arc of the sky.