Results On Tycho Photometry

The final Tycho database will contain astrometric and photometric data for about 1 million stars. Here we discuss the results of the Tycho photometric calibration for about 80% of the data acquired by the star mapper of the Hipparcos satellite and estimate the photometric precision in the final Tycho photometric data base. For a non-variable star of 7th (10th) magnitude with approximate to 100 observations a precision of better than 10 mmag (40 mmag) can be expected in the Tycho star catalogue. The precision on (B - V)(T) depends only slightly on the colour and is exptected to be better than 20 mmag (60 mmag) for the same number of observations. These results will be representative of the final Tycho photometric quality.