AGK2

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The AGK2 for Astronomical Society Catalog 2 is a star catalog of around 200,000 fixed stars , which was created in the 1930s on the initiative of the Astronomical Society as a cooperation project between several observatories.

The Astronomical Society (AG) as one of the oldest scientific associations in Europe was founded in 1800. Around 1860 she initiated the most important star catalog of this time, the AGK named after her. From 1929 it was extended to the AGK2 - with newer astrometry data and with precise consideration of the own movements . This AGK2 is up to our days (together with the newer version AGK3 ) an important database for astronomy , celestial mechanics and orbit determination .

Astrometric methodology

The measurement of the star locations of the AKG2 took place

The AGK2, which resulted from about 10 years of work, comprises over 200,000 stars (down to 9th to 10th magnitude ) and with position accuracies better than 1 ″. Up until the 1980s it was an important basis for astrometry and for evaluations in the context of satellite geodesy - and around 1960 it also became the "ancestor" of the SAO catalog with 250,000 stars.

International cooperation

A monograph by the Hamburg observatory describes the history of its creation in more detail. At the General Meeting of the Astronomical Society in Potsdam in 1921, Richard Schorr and other astronomers proposed to repeat the observations 50 years after the first AGK star catalog . The catalog of the Astronomical Society adopted in 1869 had become a standard work for sky surveying. 12 observatories from different countries participated in it from 1868–1908 and measured more than 100,000 star locations. They were published as a 15-volume work in the "Catalog of the Astronomical Society, 1st section".

The new observation from 1921 and the expansion to over 200,000 stars took place in the "Zone Company of the Astronomical Society". The new catalog of positions was particularly important because the position of the earth's axis in space is continuously changing by small portions ( precession ) and because the star positions shift over the long term within the Milky Way (proper movements).

The new star catalog was decided as a joint project of the Hamburg , Bonn and Pulkowo observatories . The recording and measuring technology was also new to the work: photo plates on special wide-angle cameras (astrographs), which then had to be measured on very precise measuring machines in the laboratory.