Henry Draper catalog
| Alternative names | HD |
|---|---|
| Survey type |
astronomical catalog 
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| Named after |
Henry Draper
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| Published | 1918
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The Henry Draper Catalogue (HD) is an astronomical star catalogue published between 1918 and 1924, giving spectroscopic classifications for 225,300 stars; it was later expanded by the Henry Draper Extension (HDE), published between 1925 and 1936, which gave classifications for 46,850 more stars, and by the Henry Draper Extension Charts (HDEC), published from 1937 to 1949 in the form of charts, which gave classifications for 86,933 more stars. In all, 359,083 stars were classified. The original HD catalogue covers the entire sky almost completely down to an apparent photographic magnitude of about 9; the extensions added fainter stars in certain areas of the sky. The construction of the Henry Draper Catalogue was part of a pioneering effort to classify stellar spectra, and its catalogue numbers are commonly used as a way of identifying stars.
The origin of the Henry Draper Catalogue dates back to the earliest photographic studies of stellar spectra. Henry Draper made the first photograph of a star's spectrum showing distinct spectral lines when he photographed Vega in 1872. He took over a hundred more photographs of stellar spectra before his death in 1882. In 1885, Edward Pickering began to supervise photographic spectroscopy at Harvard College Observatory, using the objective prism method. In 1886, Draper's widow, Mary Anne Palmer Draper, became interested in Pickering's research and agreed to fund it under the name Henry Draper Memorial. Pickering and his coworkers then began to take an objective-prism survey of the sky and to classify the resulting spectra.
A first result of this work was the Draper Catalogue of Stellar Spectra, published in 1890. This catalogue contained spectroscopic classifications for 10,351 stars, mostly north of declination −25°. Most of the classification was done by Williamina Fleming. The classification scheme used was to subdivide the previously used Secchi classes (I to IV) into more specific classes, given letters from A to N. Also, the letter O was used for stars whose spectra consisted mainly of bright lines, the letter P for planetary nebulae, and the letter Q for spectra not fitting into any of the classes A through P. No star of type N appeared in the catalogue, and the only star of type O was the Wolf–Rayet star HR 2583.
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