WARNING : the field numbers of the Main Catalogue are not identical to those of the printed version as some useful information has been added.
The description of the data given below follows the order of
the columns of the Hipparcos Input Catalogue. Further explanations, along with
relevant information on how the data were collected and selected, are included
in smaller type. Full names and references of all catalogues are given
at the end of this introduction (page ). In general, the number of
decimals retained provides an indication of the precision of the data.