Definition of the Celestial Reference Coordinate System in Fundamental Catalogues

Abstract

AbstractThe celestial reference coordinate system in fundamental catalogues is defined by the position of the celestial equator as the fundamental plane, the vernal equinox as zero point for reckoning right ascensions, and by adopted values of precession. Discussed are (1) the methods which, in practice, provide the equator, equinox and precession, (2) the prospects of progress in the direction of higher accuracy, (3) the realization. of a homogeneous system on the sky, and (4) the extension of the system to a reference frame represented by extragalactic objects.The basic observational material available for the project of an improvement of the Fourth Fundamental Catalogue (FK4) is discussed, and the plan of establishing FK5 outlined.