I/174   ==OBSOLETE version of Catalogue==
13-Jan-1997: Superseded by 4th Edition: I/238

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Beginning of ReadMe : I/174 Yale Trigonometric Parallaxes Preliminary (van Altena+ 1991) ================================================================================ The General Catalogue of Trigonometric Stellar Parallaxes, Preliminary Version van Altena W.F., Lee J.T., Hoffleit D. <Yale University Observatory (1991)> ================================================================================ ADC_Keywords: Parallaxes, trigonometric Description: The preliminary edition of the General Catalogue of Trigonometric Stellar Parallaxes, containing 15349 parallaxes for 7879 stars, has been prepared at the Yale University Observatory. In this edition 1480 stars have been added to those contained in the previous edition of the catalog by Jenkins (1952, 1963). This relatively small increase in the number of stars is more than compensated for by the increased accuracy of the newer trigonometric parallaxes. The authors have attempted to include here all trigonometric parallaxes made available to them by March 1991 and will provide for each listed parallax in the final version the reference to its source of publication. For each star it lists the equatorial coordinates for B1900 and the secular variation for 100 years, the proper motion in x and y, the weighted average absolute parallax and its standard error, the number of parallax observations, the quality of interagreement among the different values, the visual magnitude, and various cross identifications with other catalogs. The B1900 equinox has been maintained to avoid assigning yet another star number. Ancillary information, including UBV photometry, MK spectral types, data on the variability and binary nature of the stars, orbits when available, and miscellaneous information to aid in determining the reliability of the data, will be listed in the final version. The relative parallaxes are corrected to absolute parallax using newly computed corrections that are based on an improved model of the galaxy. An analysis of the resulting absolute parallaxes has been made to study the accidental and systematic errors of the parallaxes. The results of that investigation are used to arrive at a weighting system for the catalog, which then yields weighted absolute parallaxes for each star. The weighting system is still under investigation; therefore, the weighted parallaxes may change a bit in the final version. Printed copies of the catalog will be available from the Yale University Observatory when the work has been completed (late 1993?). See the file cdrom.doc which provides the original documentation by W. van Altena.