Reference frame
The Fourth Fundamental Catalogue (FK4)
The predecessor of FK5, a fundamental star frame referred to the equinox and epoch B1950. Positions given in the FK4 (B1950) system must be precessed and rotated to be compared with modern J2000/ICRS coordinates — a common source of small errors when working with older catalogues and charts.
Highlights
- ›The B1950 bright-star frame that FK5 replaced
Related systems & concepts
Across the reference systems
Knowledge connections
- Associated withThe Fifth Fundamental Catalogue (FK5)
- Associated withThe Fifth Fundamental Catalogue (FK5)
- Associated withThe B1950 Epoch
Sources
The primary and reference sources this topic draws on.
- IAUInternational Astronomical Union
Official naming, definitions, constellation boundaries, and astronomical nomenclature.