Availability and Usage
Stars contained in the main portion of the catalogue are of medium magnitude, down to about 9m (about 1/15 as bright as the faintest stars visible with the naked eye). The extensions contain stars as faint as the 11th magnitude selected from certain regions of the sky. Stars in the original catalogue are numbered from 1 to 225300 (prefix HD) and are numbered in order of increasing right ascension for the epoch 1900.0. Stars in the first extension are numbered from 225301 to 272150 (prefix HDE), and stars from the extension charts are numbered from 272151 to 359083 (prefix HDEC). However, as the numbering is continuous throughout the catalog and its extensions, the prefix HD may be used regardless as its use produces no ambiguity. Many stars are customarily identified by their HD numbers.
The Henry Draper Catalogue and the Extension were available from the NASA Astronomical Data Center as part of their third CD-ROM of astronomical catalogues. Currently, the Catalogue and Extension are available from the VizieR service of the Centre de Données astronomiques at Strasbourg as catalogue number III/135A. Because of their format, putting the Henry Draper Extension Charts into a machine-readable format was more difficult, but this task was eventually completed by 1995 by Nesterov, Röser and their coworkers, and the Charts are now available at VizieR as catalogue number III/182.
Read more about this topic: Henry Draper Catalogue
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