UK 1.2M Schmidt Telescope and the Southern Sky Survey. Part 5: An Absolute Calibration of the Night Sky Photometer of the UK 1.2M Schmidt Telescope

摘要

A comparison of parallel UBV observations obtained using the Night Sky Photometer (NSP) of the UK 1.2-m Schmidt Telescope and a photometric telescope at the same site led to recalibrations of the U-, B- and V-band surface brightness measurements of the NSP. The night sky brightness is found to be, on average, 0m15/sq arcsec brighter in both the B and V bands and 0m11/sq arsec fainter in the U band, in the new system than in the old. Absolute calibration to an accuracy of +1 0m1/sq arcsec is feasible for plates taken at field centers north of delta equiv. -65 deg, subject to the exclusion of bright field stars. A fault was discovered in the NSP electronics at the time of these tests which would appear to invalidate the calibration for delta -70 deg.