Named in memory of John Charles Duncan (1882–1967), a graduate of Indiana University, who taught astronomy at Harvard and Radcliffe until 1916 and at Wellesley until his retirement in 1950 — after which he taught for another 14 years at the University of Arizona. The first edition of his widely-used textbook appeared in 1916; the fifth edition appeared in 1955. His Lick Ph.D. thesis on the orbits of two cepheid variables was the first step toward the abandonment of the widely-held binary star theory of cepheid variation. During a 28-year association with the Mount Wilson Observatory he measured the expansion of the Crab Nebula (1921), discovered three variable stars in external galaxies (1922) and took a superb series of pictorial photographs of galaxies, nebulae and Milky Way fields. (M 12457) _ _.