Why doesn the Hipparcos www site allow interrogation according to various important cross-identifiers: BD, or CD for example?
A. Cross identification of stars is frequently complicated by the angular precision or resolution of earlier catalogues, or errors propagated in these identifiers through the literature. Some identifiers are included within the fields of the machine-readable version of the Hipparcos and Tycho Catalogues, but they should be considered more “for information”. If you know a particular star identifier, use the CDS SIMBAD facility to find the corresponding HIP number – these identifiers are maintained and updated. Or use the position of the star to search the catalogue.
