Édouard Stephan discovered NGC 5991 = St X-27 on 13 Jun 1879 and recorded "fairly faint, small, round, strong concentration in the center." His position is accurate.

400/500mm - 17.5" (4/7/89): fairly faint, very small, round, gradually increases to a very small bright core. Located 7' SSE of mag 7.5 SAO 83981, which hampers viewing somewhat.

Notes by Steve Gottlieb