The Astronomische Gesellschaft Katalog (AGK) is an astrometric star catalogue of the Northern hemisphere.
Compilation for the first version, Astronomische Gesellschaft Katalog 1 AGK1, was started in 1867, directed by Friedrich Argelander and published between 1890 (three sections from the observatories at Oslo, Helsinki, and Neuchâtel Observatory) and 1924 (final section: Algiers Observatory), listing 200 000 stars down to ninth magnitude.
[1] The second version, AGK2, was started in the 1920s, and published between 1951 and 1958 using photographic data obtained from the Bonn and Hamburg Observatories.
Karl Friedrich Küstner was involved in the planning for star catalog AGK2 with the Bonn part then directed by Ernst Arnold Kohlschütter.
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