The TYCHO Input Catalogue. Cross- matching the Guide Star Catalog with the HIPPARCOS INCA Data Base.

A Tycho Input Catalogue of three million stars brighter than V=12.1 has been produced for the needs of the Tycho data analysis. This catalogue results from the cross-matching of a subset of the Hubble Space Telescope Guide Star Catalog with the Hipparcos INCA Data Base. The cross-matching procedure is explained and statistics about the magnitude distribution and errors of the resulting catalogue are given