The Catalogue of Fundamental Stars is a series of six astrometric catalogues of high precision positional data for a small selection of stars to define a celestial reference frame, which is a standard coordinate system for measuring positions of stars.
Contents
Publication of FK4 through FK6
The Fourth Fundamental Catalogue (FK4) was published in 1963, and contained 1,535 stars in various equinoxes from 1950.0 to 1975.0 .
The Fourth Fundamental Catalogue's Supplement (FK4S) was an amendment to FK4 that contains a further 1,987 stars.
The Fifth Fundamental Catalogue (FK5) was a 1988 update of FK4 with new positions for the 1,535 stars. It was superseded by the quasar-based International Celestial Reference Frame (ICRF).
The Fifth Fundamental Catalogue Extension (FK5), published in 1991, added 3,117 new stars.
The Sixth Fundamental Catalogue (FK6) is a 2000 update of FK5 correlated with the ICRF through the Hipparcos satellite. It comes in two parts: FK6(I) and FK6(III). FK6(I) contains 878 stars, and FK6(III) contains 3,272 stars. Both are updated and amended versions of FK5, using Hipparcos catalogue data.