1.2.2 Polarimetry of the Zodiacal Light and Milky Way from Hawaii

Extract

This paper describes the results of a program of observations of the polarized intensity vector of the night sky in the anti-solar hemisphere obtained on 72 nights between May 1973 and November 1974. The observations were made with the night sky polarimeter at Mt. Haleakala, Maui, Hawaii, using a 5300A interference filter, 62A wide, to define the passband. They were made at fixed altitudes from 35° to 90° along the north-south meridian and repeated in sequence throughout the night. The diameter of the field of view was 6.0° and the integration time per point was either 30 or 120 seconds. Polarization was detected using a rotating polaroid (11 1/4 revs sec⁻¹); the signal from the polaroid drive generator provided a phase trigger allowing the photo-multiplier signal to accumulate and be digitized for each of the four 90° phase intervals of the polarization modulation cycle. This process continued for the entire integration period. The digitization and data handling and recording (paper tape and teletype) was carried out by a PDP-81 computer, and calibrated Stokes parameters (I, Q, U) and the polarized intensity pI were calculated later. Intensity calibration in S₁₀ (V, G2V) units was obtained using a C₁₄ low brightness source, and the amplitude and phase of the polarization modulation were checked each night.