Precessional correction and the proper-motion systems of FK5 and Hipparcos

Abstract

Comparing proper motions of the FK5 and Hipparcos, several authors declared that the two proper-motion systems are inconsistent with the value of the precessional correction obtained from VLBI and LLR observations. Based on the proper-motion data from the PPM and ACRS catalogues which are constructed on the FK5 system, the discrepant values of the precessional correction and of the correction of the equinoctial motion, derived from the different subsets of stellar samples, have be found. One of the reasons for those discrepancies should be mostly due to the internal biased proper-motion system of the FK5.