Friedrich Wilhelm August Argelander

Friedrich Wilhelm August Argelander , 1799-1875, German astronomer. He became director of the observatory at the Univ. of Bonn in 1837 and continued there the work of determining the positions of stars that F. W. Bessel had begun at Königsberg. The results of his observations appear in the Bonner Durchmusterung (1862), which records the positions and brightness of more than 324,000 stars (up to the ninth magnitude) in the northern heavens.

Argelander, FriedrichWilhelmAugust (1799–1875)Germanastronomer, born in modern Lithuania. From a study of the proper motions of several hundred stars he confirmed F. W.Herschel's calculated position of the Sun's apex. His main achievement, begun in 1852, was a survey of all stars down to 9th magnitude in the northern hemisphere. The resulting star atlas and catalogue were published in 1859–62 as the Bonner Durchmusterung. He subsequently initiated the first AGK catalogue. Argelander also introduced the subdivision of magnitudes into tenths, the step method for estimating stellar magnitudes, and the practice of assigning capital roman letters to variable stars.