Secchi, Angelo

Born June 29, 1818, in Reggio nell’Emilia; died Feb. 26, 1878, in Rome. Italian astronomer.

Secchi became director of the observatory at the Roman College in 1849. He is best known for his investigations of the spectra of stars, the sun, the moon, the planets, and comets. In 1863, Secchi made the first classification of stellar spectra. His division of the spectra into four groups was generally accepted until the introduction of the Harvard classification in the mid-20th century. Secchi was one of the first investigators to apply photography to astronomy. He also worked in the areas of geodesy, meteorology, and hydrology. He developed an instrument—the Secchi disk—for measuring water transparency.