Édouard Stephan discovered NGC 6640 = St XIII-89 on 21 Aug 1884. His position is accurate.
400/500mm - 17.5" (7/7/94): faint, small, elongated 3:2 NNW-SSE, 0.9'x0.6', weak concentration. A mag 14.5 star is close east of the core, a mag 13.5 star is 1.5' N and a mag 11 star is 4.0' SSE.
Notes by Steve Gottlieb