HDEC - Henry Draper Extension Charts 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 is available at the legacy anonymous ftp site (legacy.gsfc.nasa.gov) in the directory heasarc/dbase/misc_files/hdec as the file hdec.remarks. If the parameter `Remarks' is set to 'R' for an entry in the HDEC database, this means that there is a remark about that particular star in the above file.
The name of the star, constructed by concatenating the prefix `HD' , the HD number, and the component identification (if any). Notice that the IAU Dictionary of Astronomical Nomenclature recommends the prefix HD rather than HDE for stars in the HDEC.
The HD number of the star: notice that stars in the HDEC have HD numbers in the range [272151/359083] inclusive.
The right ascension of the star. For those stars for which proper motions were known, the epoch of the position is J2000.0. If the star was identified with either an AC or a GSC star (i.e., there is no known proper motion), the position is given at the corresponding epoch of observation (specified by the parameter observing_epoch). The modern-epoch positions have a typical accuracy of 0.45 arcseconds.
The declination of the star. For those stars for which proper motions were known, the epoch of the position is J2000.0. If the star was identified with either an AC or a GSC star (i.e., there is no known proper motion), the position is given at the corresponding epoch of observation (specified by the parameter observing_epoch). The modern-epoch positions have a typical accuracy of 0.45 arcseconds.
The galactic longitude of the star.
The galactic latitude of the star.
The component identification for multiple systems using the usual notation A, B, C, D, E, F. Notice that stars in multiple systems are given the same HD number.
A parameter that is set to 'R' if there is an individual remark for this star given in the 'remarks' file. This latter file is not part of the current database but can be obtained from the legacy anonymous ftp site (legacy.gsfc.nasa.gov); it is in the directory heasarc/dbase/misc_files/hdec as the file hdec.remarks.
The HD spectral class of the star.
The apparent magnitude of the star: this is the photographic B-magnitude taken from the Astrographic Catalog (AC) (for those entries having the parameter position_source = "P", "A" or "C"), or the Guide Star Catalog J or V magnitude (for those entries having the parameter position_source = "G"). The typical accuracy of these magnitudes is 0.3 mag.
A flag referring to the catalog from which the star position was obtained: "P" = the PPM Star Catalog, "C" = the Guide Star and Astrographic Catalogs (GSC-AC), "A" = the Astrographic Catalog (AC), "G" = the Guide Star Catalog (GSC), "M" means that no identification with any of teh above-listed catalogs was possible, and that the position given is a reduced measured one, and "V" means that the position was taken from either the General Catalog of Variable Stars (GCVS) or the Catalog of Suspected Variable Stars (CSVS).
A flag that is set to "T" if proper motions are given, but set to "F" if only a position at a single epoch is known.
The annual proper motion in RA, in units of arcseconds per year. The typical rms error of the total proper motion is 5.5 mas per year.
The annual proper motion in Dec, in units of arcseconds per year. The typical rms error of the total proper motion is 5.5 mas per year.
For those stars for which only a single observation is available, this parameter contains the observation epoch in Julian years.
The browse classification of the star, derived from its listed spectral type.