Survey (astronomy)

In astronomy, a is Survey the screening of the sky or a sky certain section. It takes place in the sense of the above 3rd meaning up to a certain limit brightness of the stars or other objects. In the past, the star locations were mainly measured on meridian circles, of which there are electro-optical ones today. From 1900 special photo plates came into use, and from around 1985 the CCD technology. The brightness is determined on the basis of the blackening or by means of photometry . Important quality features are: the uniformity of the recorded photo plates or scans, their scale (focal length), the light intensity (limit brightness) and the lowest possible distortion of the optics.

The three most popular astronomical surveys are:

• the Bonn survey (visually measured locations of 325,000 stars), published in 1855 by the University of Bonn in the form of a star catalog and associated star maps
• the Palomar Sky Survey with thousands of blue- and red-sensitive plates, publ. around 1950 and still widely used today, e.g. B. for galaxies or when determining the orbit of newly discovered asteroids
• the 1997 Hipparcos catalog , of which the astrometry satellite HIPPARCOS measured 108,000 stars to within ± 0.003 ''; a second Tycho catalog even contains 1 million stars (less precise).