William Herschel discovered NGC 3990 = H II-791 = h1029, along with NGC 3998, on 14 Apr 1789 (sweep 920) and recorded both as "Two, the last NGC 3998] cB or vB, R, vgbM. The preceding [NGC 3990] pB, E, S."

400/500mm - 17.5" (4/6/91): fairly faint, very small, slightly elongated SW-NE, small bright core. Forms a pair with NGC 3998 2.9' E. Located 4.4' S of mag 9.2 SAO 28204.

Notes by Steve Gottlieb