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PPM Catalog: Catalog Help


Overview

The PPM Star Catalog ( Roeser, S., Bastian, U., 1991, Astronomisches Rechen-Institut, Heidelberg, Vols. I and II, printed by Spektrum Akademischer Verlag, Heidelberg) provides a convenient, dense and accurate net of 378,910 astrometric reference stars. The net is designed to represent as closely as possible the IAU (1976) cooordinate system on the sky, as defined by the FK5 star catalogue (Frick et al., 1988). Thus, the PPM is an extension of the FK5 system to higher star densities and fainter magnitudes.

The PPM can be considered a replacement of two preceding astrometric catalogs which served a similar purpose: AGK3 and the SAO Catalog. In contrast to the PPM, these older catalogs are based on (1) the now obsolete FK4 system of positions and proper motions, and (2) only two position measures per star.

The files PPM and PPMra each contain the entire PPM Catalog of 378910 stars, including B1950 positions (accurately converted from J2000), proper motions, magnitudes, and spectral types (usually) in a locally-developed binary format. While the SAO catalog is more or less complete to V=9, with 4,503 stars fainter than V=10, the PPM catalog is fairly complete to V=9.5, with 102,672 stars fainter than V=10 and 22,395 stars fainter than V=11.

A supplemental catalog which guarantees completeness to V=7.5 has not yet been added at this site. Regarding completeness, the intent of the PPM supplemental list is to render the PPM complete to magnitude V=7.5. For fainter magnitudes, the supplemental list documentation states that,

... of the perhaps 20 000 stars between V=7.5 and V=8.5 only a few hundred are missing from PPM. So, the combined PPM can be considered as practically complete to at least V=8.5. In photographic magnitudes this corresponds to roughly 9 mag.

An ASCII version with more information for each star is available from NASA's High Energy Astrophysics Science Archive Research Center (HEASARC) at ftp://legacy.gsfc.nasa.gov/heasarc/dbase/dump/heasarc_ppm.tdat.gz. 275 missing stars with V < 7.6 (The Bright Stars Supplement to the PPM and PPM South Catalogue, Revised Edition Bastian U. and Roeser S. 1993. Astronomisches Rechen-Institut, Heidelberg) are included. Online documentation is available at http://heasarc.gsfc.nasa.gov/W3Browse/star-catalog/ppm.html.


 
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