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Description
This catalogue lists improved mean positions and proper motions for the 995 stars in the FK4 Supplement (Veroeff. Astron. Rechen-Inst. Heidelberg No 11, 1963) which were not included in the Fifth Fundamental Catalogue (Part I: "The Basic FK5", Fricke et al., 1988, Veroeff. Astron. Rechen-Inst. Heidelberg No 32, Catalogue I/149/; Part II: "The FK5 Extension", Fricke et al., 1991, Veroeff. Astron. Rechen-Inst. Heidelberg No 33, Catalogue I/175/). The main purpose of the FK4 Supplement was to stimulate further observations within absolute and differential programs of the stars listed in that catalogue with the aim of their inclusion as new fundamental stars into a future fundamental catalogue. The new fundamental stars should increase the star density without extending the magnitude limit to fainter magnitudes. Since the publication of the "Supplement-Katalog des FK3" (published in Astron-Geodaet. Jahrbuch 1954 and Astron-Geodaet. Jahrbuch 1956) these stars were included in many observing programs. Within work on deriving the FK5 Extension all stars in the FK4 Supplement had been treated in exactly the same way and improved mean positions and proper motions had thus been obtained for all FK4 Sup stars. For more details reference is made to the introduction of the FK5 Extension. FK4 Sup stars with the best astrometric data were included in the FK5 Extension for achieving a homogeneous distribution in magnitude and taking simultaneously into account an even distribution on the sky. This selection process included 992 of the 1987 FK4 Sup stars into the FK5 Extension. Although the astrometric precision of the stars given in the present catalogue is inferior to that of the FK4 Supplement stars included in the FK5 Extension, they deserve being published because a considerable number of observations has been obtained for these stars since about 1955, stimulated by the publication of the FK3 Supplement. The average mean epoch of observation of the stars given is therefore shifted to comparatively modern epochs (see the table in Section 2 of the publication). The astrometric precision of the stars presented here is better than for most other published star positions and proper motions, and the positions and proper motions are the best which could be derived from the available observations. These observations are published in the same catalogues as listed in the FK5, Part II on pages 139 ff. The apparent visual magnitudes are between 3.6 and 7.7 with a concentration around the mean value of 5.94. They are thus within the magnitude limit of the Basic FK5.
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