Abbreviation for the star catalogue Astronomische Gesellschaft Katalog. The first project, for cataloguing all stars between declinations -2° and +80° down to ninth magnitude, was initiated by F. W. Argelander in 1867. Seventeen observatories participated and the fifteen volumes of AGK1 listed 150,000 stars. An extension to declination -23° published in 1887 contained a further 50,000 stars. A second version was started in the 1920s, using photography rather than visual observations, and was published in 1951-58. Measurements of proper motions were included in the third version, AGK3. AGK positions are accurate positions, calculated relative to fundamental stars. See also: