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Description
The present version of the CNS3 contains all known stars within 25 parsecs of the Sun. It depends mainly on a preliminary version (Spring 1989) of the new General Catalogue of Trigonometric Parallaxes (YPC) prepared by Dr. William F. van Altena (Yale University). The catalogue contains every star with trigonometric parallax greater than or equal to 0.0390 arcsec, even though it may be evident from photometry or for other reasons that the star has a larger distance. For red dwarf stars, new color-magnitude calibrations for broad-band colors were carried out and applied. For white dwarfs, the recipes of McCook and Sion were applied (=1985ApJS...65..603M). Stroemgren photometry was used (not yet systematically) for early-type stars and for late dwarfs, the latter supplied by E. H. Olsen from Copenhagen Observatory (private communication). Contrary to the CNS2 (Gliese 1969) trigonometric parallaxes and photometric or spectroscopic parallaxes were not combined. The resulting parallax in the present version is always the trigonometric parallax -- if the relative error of the trigonometric parallax is smaller than 14 percent. The resulting parallax is the photometric or spectroscopic parallax only if no trigonometric parallax is available or if the standard error of the trigonometric parallax is considerably larger.
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