Further Astrometric Observations with the 5-km Radio Telescope

Abstract

Positions of 53 compact extragalactic and two galactic sources have been determined in order to provide a basis for a radio astrometric system for the northern sky. Declinations are measured absolutely with an accuracy of |$\approx \pm 0^{\prime\prime} \cdot 03$| arc at δ = 45° and relative right ascensions are determined to within a few milliseconds. The zero point of right ascension has been established relative to the FK4 position of β Persei with an accuracy of ± 1·5 ms; recent optical measurements have confirmed the FK4 catalogue position to within ± 4 ms. Earlier 5-km telescope results have been corrected for a mistake in the computation of diurnal aberration and a number of improvements have been incorporated, which include a more refined model for the atmosphere and better corrections for instrumental effects due to temperature variations.