Polarisation in the night sky at 5,300 Å

Abstract

WE have presented observations¹ of the linearly polarised intensity, pI, at 5,080 Å (that is, polarisation, p × intensity, I), of radiation in the night sky. Contour plots of pI showed a displacement of the minimum of pI away from the antisolar point (ASP). A significant angular structure, and day-to-day variations were also evident. Here, we report observations of pI and of the orientation angle, χ, of the polarisation plane of radiation at 5,300 Å in the night sky. Measurements have been taken since May 1973 with a photoelectric polarimeter at the University of Hawaii (J. L. Weinberg, unpublished). Several modifications have been made recently, the most important being the analog–digital conversion of data recording. Digitisation allows faster data reduction and improves measurement precision, which is now limited by instrumental polarisation and photon statistics. Full data will be published elsewhere; here, we discuss 63 nights of observation from May 1973–June 1974.