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Description
The Henry Draper (HD) Catalog (Cannon and Pickering 1918 - 1924, Ann. Astron. Obs. Harvard College 91 - 99) and its first extension, the Henry Draper Extension (HDE) Catalog (Cannon 1934, Ann. Astron. Obs. Harvard College 100, 1 - 6), provided spectral classification and rough positions for 272,150 stars and has been widely made use of by the astronomical community for over half a century. A second extension of the HD Catalog, the so-called Henry Draper Extension Charts (HDEC), subsequently extended this spectral classification to fainter magnitudes (Cannon 1937, Ann. Astron. Obs. Harvard College 105, 1; Cannon and Mayall 1949, Ann. Astron. Obs. Harvard College 112), thus adding nearly another 87,000 stars with derived spectral types. The information in the HDEC was published in the form of charts rather than tables like the HD and HDE Catalogs, and consequently has been barely utiized by modern astronomers. In the 1990's, after a pilot project of Roeser et al. (1991, Astr. Ap. Suppl., 88, 277) had demonstrated that it seemed feasible to `revive' the HDEC data, they were converted into a catalog of accurate astrometric parameters along with magnitudes and spectral types by Nesterov et al. (1995, Astr. Ap. Suppl., 110, 367), who used measurements of Cartesian coordinates of stars in the charts and the positions in the Astrographic Catalog (AC) for subsequent cross-identification. The Nesterov et al. (1991) reference should be consulted for the full details on the procedures used to create this HDEC catalog. The HDEC catalog contains information on 86,933 stars, comprising accurate (0.5 arcseconds error) positions, (for more than 96 per cent of them) proper motions with a typical accuracy of 5.5 milliarcseconds (mas) per year, and the original spectral classifications. The current database contains the main portion of the catalog. An additional set of information, primarily comprising HD entries with cross-identifications with known or suspected variable stars, was included in the A.J. Cannon Memorial Volume (Cannon and Mayall 1949). This list was extended by Nesterov et al. (1991) to more than 500 identifications with variable stars. This latter expanded list, together with a list of entries which have uncertain identifications, is not included in the HEASARC version of this catalog, but it is available on the HEASARC website in the directory <a href="/FTP/heasarc/dbase/misc_files/hdec/">/FTP/heasarc/dbase/misc_files/hdec/</a> as the file <a href="/FTP/heasarc/dbase/misc_files/hdec/hdec.remarks">hdec.remarks</a>. If the parameter "remarks" is set to "R" for an entry in the HDEC catalog, this means that there is a remark about that particular star in the above file. This database was created by the HEASARC in April 1998 based on the machine-readable ADC/<a href="https://cdsarc.cds.unistra.fr/ftp/cats/III/182">CDS Catalog III/182</a>. This is a service provided by NASA HEASARC .
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