The Tycho-2 Catalogue
The Tycho-2 Catalogue is an astrometric reference catalogue containing positions, proper motions and two-colour photometry for the 2.5 million brightest stars in the sky. The catalogue is based on observations made using the Hipparcos satellite star mapper and is constructed using the same observations that were used to create the original Tycho catalogue. Improved reduction techniques have resulted in a catalogue with significantly more entries and in improved precision.
Details of the data reduction, catalogue construction and verification of the results can be found in "Construction and verification of the Tycho-2 Catalogue", E. Høg, C. Fabricius, V.V. Makarov, et al., A&A, 357, 367-386 (2000).