Americanastronomer and optician. At Mount Wilson Observatory he made the mirror for the 60-inch (1.5-m) telescope and supervised the work on the mirror for the 100-inch (2.5-m). With these instruments he discovered dark lanes in the Andromeda Galaxy, and in 1917 he took the first photographs of novae and supernovae in the Andromeda Galaxy, providing the first means of estimating its distance. He also took the first photographs to show globular clusters around other galaxies. He later collaborated on the design of the Ritchey–Chrétien telescope, the first of which was completed in 1930.
Subjects: Astronomy and Astrophysics.