The Berliner Astronomisches Jahrbuch (abbrev. B.A.J.) is an astronomical ephemeris almanac and the longest publication series in astronomy. It was a compendium of ephemerides of all large Solar system bodies and of fundamental stars which define the celestial reference system.
The B.A.J. series began in 1776 and continued until 1960 when it was included into the international edition of the Astronomical Ephemeris and of Apparent Places of Fundamental Stars (APFS). This merger was decided in 1959 by the IAU.
At least the Yearbook had a volume of about 500 pages; starting in 1907 it contained accurate apparent places of the first international fundamental catalogue which was compiled for astrometry; later these data were actualized within the framework of the Catalogues of Fundamental Stars FK3 and FK4.
In the 1940s the Almanac was edited in co-operation with the Astronomisch-Geodätisches Jahrbuch of the Recheninstitut in Heidelberg, Germany, which was merged also into the IAU editions like other national almanacs.