Durchmusterung

In astronomy, Durchmusterung or Bonner Durchmusterung (BD), is the comprehensive astrometric star catalogue of the whole sky, compiled by the Bonn Observatory (Germany) from 1859 to 1903. In astronomy, Durchmusterung or Bonner Durchmusterung (BD), is the comprehensive astrometric star catalogue of the whole sky, compiled by the Bonn Observatory (Germany) from 1859 to 1903. The name comes from Durchmusterung ('run-through examination'), a German word used for a systematic survey of objects or data. The term has sometimes been used for other astronomical surveys, including not only stars but also the search for other celestial objects. Special tasks are the celestial scanning in electromagnetic wavelengths which are shorter or longer than visible light waves. The 44 years work of the Bonner Durchmusterung (abbreviated by BD) resulted in a catalogue giving the positions and apparent magnitudes of approximately 325,000 stars to apparent magnitude 9–10. It was the basis for an excellent star atlas (some 100 pages) and for the AGK and SAO catalogues of the 20th century. The BD star numbers are still used and allow the correlation of this pioneering work with modern projects. The format of a BD number is exemplified by BD−16 1591 which is the BD number of Sirius. This number signifies that in the catalog Sirius is the 1591st star listed in the declination zone between −16 and −17 degrees, counting from 0 hours right ascension. Stellar positions and zone boundaries use an equinox for the epoch of B1855.0. Many astronomical research projects — from studies of celestial mechanics and the solar system, up to the nascent field of astrophysics — were made possible by the publication of the Atlas and data of the Bonner Durchmusterung. However, a deficiency of the BD was that it did not cover the whole sky, because far southern stars are not visible from Germany. This led the scientific community to supplement the BD by two additional astrometric surveys carried out by observatories located at the Southern hemisphere: Córdoba, Argentina, and Cape Town, South Africa.The Cordoba Durchmusterung (abbreviated CD, or, less commonly, CoD) was made visually (as was the BD), but the Cape Photographic Durchmusterung (CPD) was conducted by the then new photographic technique, which had just been shown to have sufficient accuracy.The southern stars are identified by CD and CPD numbers in a manner similar to the BD numbering system. A few decades later the positional accuracy of the Durchmusterung catalogues began to be insufficient for many projects. To establish a more exact reference system for the Bonner Durchmusterung, in the late 19th century the astronomers and geodesists began to work on a Celestial Fundamental Co-ordinate System, based on the Earth's rotation axis, the vernal equinox and the Ecliptic plane. This astrometric project led to the Fundamental Catalogue of the Berlin observatory and was used as an exact coordinate frame for the BD and AGK. It was modernized in the 1920s (FK3, mean accuracy ±1'), up to the present FK6 as the latest step of cosmic geodesy (accuracy 0.1'). Together with radioastronomical measurements the FK6 accuracy is now better than ±0.1'. The most important modern development has been the Hipparcos satellite, operated between 1989 and 1993, which observed around 118,000 stars over the whole sky, and led to three very accurate star catalogues: The Gaia space observatory, launched in December 2013, is planned to provide the next advancement in astrometry. It is in the process of cataloguing a billion stars with an accuracy down to 20 microarcseconds (0.00002').