Ritchey, George Willis, 1864–1945, American astronomer, b. Meigs co., Ohio, studied at the Univ. of Cincinnati (1883–84, 1886–87). He was superintendent of instrument construction (1899–1904) at Yerkes Observatory and then (1905–9) was associated with the Solar Observatory of Carnegie Institution. From 1901 to 1905 he taught astronomy at the Univ. of Chicago. Ritchey was in charge of the designing and construction of the 60-in. (152-cm) and 100-in. (254-cm) reflecting telescopes at Mt. Wilson Observatory. Later he went to the Paris Observatory as director (1924–30) of the astrophotographic laboratory. He is coinventor of the Ritchey-Chrétien reflecting telescope, and he supervised (1931) the construction of a 40-in. (102-cm) telescope of that type for the U.S. Naval Observatory. The cellular type of optical mirror was also his invention.