Selected areas
The Selected Areas are systematically applied calibration fields of astronomy for the purposes of galactic stellar statistics . They go back to a proposal by Jacobus Kapteyn (University of Groningen) and were gradually established by several large observatories from around 1910. The major project, also known as Kapteyn's calibration fields , contains
- 206 star fields distributed regularly and symmetrically to the galactic equator with an extent of 1.25 ° × 1.25 °
- and an additional 46 fields in special areas of the Milky Way.
In them all accessible stars were counted and examined for their physical and kinematic properties. They are considered representative samples for the entire sky.
The Selected Area No. 1 corresponds to the north polar sequence , No. 26 to the star cluster of the Pleiades .
Observatories and results
The participating observatories included the Harvard and Mount Wilson observatories , in Germany also Hamburg-Bergedorf and the Astrophysical Institute Potsdam .
In the representative survey , around 250,000 stars were recorded - with star words , intrinsic movements, parallaxes, spectral classes and, above all, brightness. The photometry of the Harvard and Mt.Wilson observatories reached limit brightnesses of 16 and even 18 mag. The data were published between 1918 and 1924.
literature
- Günter D. Roth: Kosmos Astronomiegeschichte , chapter "Progressive inventory of the sky". Kosmos-Verlag, Stuttgart 1987
- H. Zimmermann, A. Weigert: Lexicon of Astronomy . Spektrum-Verlag, Heidelberg-Berlin 1999
- Dieter Herrmann: The Milky Way. Stars, nebulae, star systems , p. 108ff. Kosmos Astrobibliothek, Stuttgart 2003