Astronomische Gesellschaft Katalog
Encyclopedia
The Astronomische Gesellschaft Katalog (AGK) is an astrometric star catalogue
. Compilation for the first version, AGK1, was started in 1861 by Friedrich Argelander and published between 1890 and 1954, listing 200 000 stars down to ninth magnitude
.
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.
The third version, AGK3, was started in 1956 and published in 1975. It contains 183,145 stars north of declination
–2° with mean positional errors of ±0.13" and mean proper motion
errors of ±0.009"/year.
Star catalogue
A star catalogue, or star catalog, is an astronomical catalogue that lists stars. In astronomy, many stars are referred to simply by catalogue numbers. There are a great many different star catalogues which have been produced for different purposes over the years, and this article covers only some...
. Compilation for the first version, AGK1, was started in 1861 by Friedrich Argelander and published between 1890 and 1954, listing 200 000 stars down to ninth magnitude
Apparent magnitude
The apparent magnitude of a celestial body is a measure of its brightness as seen by an observer on Earth, adjusted to the value it would have in the absence of the atmosphere...
.
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.
The third version, AGK3, was started in 1956 and published in 1975. It contains 183,145 stars north of declination
Declination
In astronomy, declination is one of the two coordinates of the equatorial coordinate system, the other being either right ascension or hour angle. Declination in astronomy is comparable to geographic latitude, but projected onto the celestial sphere. Declination is measured in degrees north and...
–2° with mean positional errors of ±0.13" and mean proper motion
Proper motion
The proper motion of a star is its angular change in position over time as seen from the center of mass of the solar system. It is measured in seconds of arc per year, arcsec/yr, where 3600 arcseconds equal one degree. This contrasts with radial velocity, which is the time rate of change in...
errors of ±0.009"/year.