Information on resource 'The Sixth Fundamental Catalogue (FK6)'

Parts I and III of the sixth fundamental catalog, a catalog of high-precision astrometry for bright stars combining centuries of ground-based observations as reflected in FK5 with HIPPARCOS astrometry. The result contains, in particular for the proper motions, statistically significant improvements of the Hipparcos data und represents a system of unprecedented accuracy for these 4150 fundamental stars. The typical mean error in pm is 0.35 mas/year for 878 basic stars, and 0.59 mas/year for the sample of the 3272 additional stars.


The FK5 consists of observations coming from the past 200 years. Three parts were published giving the results of that work: First we have the Basic FK5 with 1535 stars, second the FK5 Extension with 3117 objects , and third the FK5 Supplement with 995 objects.

The results from the HIPPARCOS mission were published in 1997 (The Hipparcos and Tycho Catalogues).

The catalogue

The combination of the Hipparcos data and the FK5 was primarily done using only probable single stars. Two parts were published:

In FK6 part I (published 1999) 878 single stars (or objects that could be treated as single) were used from the Basic FK5, in FK6 part III (published 2000) 3272 single stars (or objects that could be treated as single) from the FK5 Extension and the FK5 Supplement were added.

The FK6 catalogue gives three solutions for each star: Besides the standard model for single stars, in which these were treated with a constant space velocitiy (single star mode, "SI"), two further solutions were added. The data of the standard single star mode "SI" are valid for real single stars only. For all other samples of stars it is, however, necessary to include the statistically significant influence of stars with companions in the solutions. The principles of this statistical astrometry were described by 1997A&A...325..367W and are also given in the printed FK6 catalogues.

The uncertain knowledge of the included correlations allows merely to produce two approximate solutions for short-period predictions of the position (short term prediction, "STP") or predictions for longer terms (long term predictions, "LTP"). The data of the STP mode should be used for epochs near to 1991.25, the mean observational epoch of Hipparcos, the data from the LTP mode for epochs differing from this mean epoch by more than 10-20 years.

Note that part II of the catalog (containing binary stars with orbits) was never published. See 2000A&A...360..399W for an orbit of Polaris.

Abbreviations used in the notes for the objects

binarity is assumed optical since objects are approximately fixed
binarity is assumed optical since objects show no common proper motion
binarity is assumed optical since objects have a high relative velocity
binarity is assumed optical since objects have large spatial separation
no relative position given
only one observation given in CCDM or WDS (hence no relative proper motion available)

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