This unprepossessing 78-mm refractor looks as if it would make a nice comet seeker. In fact, it had an enormous impact on a century of astronomy. This was the instrument used by Friedrich Wilhelm Argelander in compiling his great star catalog, the Bonner Durchmusterung or simply the BD. This work listed 324,000 stars from the north celestial pole to just south of the equator, broken out into 1-degree striops of declination. He worked by setting the telescope to a targeted declination, and stamping his foot to mark the transit time of each star while calling out information on the star's declination to a colleague in a lighted room below.

The BD was the basis of last of the great star atlases to be compiled before the advent of photography. The catalog, originally published in three sections from 1859-1862, was superseded only by the publication of the Smithsonian Astrophysical Observatory atlas a century later. Many objects are still most commonly known by their BD numbers, which include a declination zone and running sequence number (as in the planetary nebula BD +30° 3639 in Cygnus). The BD also included the nuclei of the Andromeda Galaxy and at least two Seyfert galaxies,

Last changes: 4/2007	  © 2007