Abbr. for Fundamentalkatalog, one of a series of catalogues of positions and proper motions of fundamental stars published in Germany. The first appeared in 1879 and was intended to provide reference positions for the AGK catalogues. The second FK (the NFK) appeared in 1907. FK3 followed in 1937–8 with FK4 in 1963 and FK5 in 1988, all three of which contained 1535 stars brighter than about visual magnitude 7.5. An extension to the FK5, containing a further 3117 stars down to magnitude 9.5, was published in 1991, with a supplement containing 995 stars in 1993. The latest in the series, the FK6, is a combination of Hipparcos data and ground-based data published in two parts in 1999 and 2000, containing 878 and 3272 stars respectively. The FK4, FK5, and FK6 are published by the Astronomisches Rechen-Institut, Heidelberg.

http://cdsarc.u-strasbg.fr/viz-bin/Cat?cat=I%2F264 Detailed description and full catalogue downloadable from the CDS.

http://wwwadd.zah.uni-heidelberg.de/datenbanken/fk6/index.php.en Information page at Heidelberg University.