1799-1875

German astronomer who completed a survey of the heavens that included data on the positions and brightnesses of over 324,000 stars. His catalog, called the Bonner Durchmusterung, included more precise data on the brightnesses of stars than previous catalogs, aiding astronomers who studied variations in stellar brightness. He himself studied variable stars and devised a method for estimating their brightnesses. He also confirmed William Herschel's findings on the motion of the sun.