The TYCHO Reference Catalogue

The Tycho Reference Catalogue\ (TRC) contains high-quality positions and proper motions for 990 182\ stars of the Tycho Catalogue. The proper motions were derived from Tycho positions and Astrographic Catalogue\ positions reduced to the Hipparcos system. The median accuracy of the TRC position components is 40 mas at J1991.25. The median precision of the proper motion is about 2.5 mas/yr\ . Systematic errors are less than about 1.0 mas(/yr). The quality of the proper motions in TRC is assessed by comparison with the Hipparcos and Tycho Catalogues. Comparison with the recent ACT Catalogue which is based on an independent reduction of the same observations as used for the TRC is reported. Based on observations made with the ESA Hipparcos astrometry satellite, and on work by the Tycho Consortium in collaboration with the INCA, FAST and NDAC Consortia.