Some Considerations in Making Full Use of The Hipparcos Catalogue

Abstract

This contribution is intended as a ‘rough guide’ to the Hipparcos Catalogue for the non-expert user. We shall focus here on the interpretation of the measured parallaxes in terms of distances and luminosities of stars, and on the use of the covariance matrix of the errors on the astrometric parameters. Issues not addressed here are the level at which one may expect systematic errors to occur in the Hipparcos Catalogue, and the correlation of astrometric parameters over a given region of the sky. For more details on the latter two subjects we refer to the documentation of the Hipparcos Catalogue (ESA, 1997) and to Brown et al. (1997). We note that at present the Hipparcos Catalogue contains no identified systematic errors.