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 Anna 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. Maury used classifications numbered from I to XXII; groups I to XX corresponded to subdivisions of the Draper Catalogue types B, A, F, G, K, and M, while XXI and XXII corresponded to the Draper Catalogue types N and O. She was the first to place B stars in their current position, prior to A stars, in the spectral classification. In 1890, the Harvard College Observatory constructed the
Boyden Observatory in
Arequipa,
Peru in order to study the sky in the
Southern Hemisphere, and a study of bright stars in the southern hemisphere was published by
Annie Jump Cannon and Pickering in 1901. Cannon used the lettered types of the
Draper Catalogue of Stellar Spectra, but dropped all letters except O, B, A, F, G, K, and M, used in that order, as well as P for planetary nebulae and Q for some peculiar spectra. She also used types such as B5A for stars halfway between types B and A, F2G for stars one-fifth of the way from F to G, and so forth. Between 1910 and 1915, new discoveries increased interest in stellar classification, and work on the
Henry Draper Catalogue itself started in 1911. From 1912 to 1915, Cannon and her coworkers classified spectra at the rate of approximately 5,000 per month. The catalogue was published in 9 volumes of the
Annals of Harvard College Observatory between 1918 and 1924. It contains rough positions, magnitudes, spectral classifications, and, where possible, cross-references to the
Durchmusterung catalogs for 225,300 stars. The classification scheme used was similar to that used in Cannon's 1901 work, except that types such as B, A, B5A, F2G, and so on, had been changed to B0, A0, B5, F2, and so on. As well as the classes O through M, P was used for nebulae and R and N for
carbon stars. Pickering died on February 3, 1919, leaving 6 volumes to be overseen by Cannon. Cannon found spectral classifications for 46,850 fainter stars in selected regions of the sky in the
Henry Draper Extension, published in six parts between 1925 and 1936. She continued classifying stars until her death in 1941. Most of these classifications were published in 1949 in the
Henry Draper Extension Charts (the first portion of these charts was published in 1937.) These charts also contained some classifications by
Margaret Walton Mayall, who supervised the work after Cannon's death. The catalogue and its extensions were the first large-scale attempt to catalogue
spectral types of stars, and its construction led to the
Harvard classification scheme of stellar spectra which is still used today. ==Availability and usage==