William Herschel discovered NGC 3091 = H II-293 = h3215 on 7 Feb 1785 (sweep 368) and recorded "pB, S, bM, iR." JH called this galaxy "pB; pS; the preceding of two [with NGC 3096].

300/350mm - 13.1" (4/10/86): moderately bright, small, round, very bright core, substellar nucleus, very faint star close NW. Brightest in HCG 42.

400/500mm - 17.5" (3/28/87): bright, moderately large, very small bright core, slightly elongated halo NW-SE. A 14th magnitude "star" 1.3' NW is actually the compact galaxy MCG -03-26-006. Brightest in HCG 42 including NGC 3096 4.7' SE.

600/800mm - 24" (2/9/13): very bright, fairly large, oval 4:3 NNW-SSE, sharply concentrated with a very bright core and a very large fainter halo, extending ~2'x1.5'. HCG 42C, just off NW edge of the halo, appeared moderately bright, fairly small, round, 20" diameter, high surface brightness, brightens to the center.

900/1200mm - 48" (4/1/11): extremely bright, large, oval 4:3 NNW-SSE, ~2.2'x1.5', sharply concentrated with a brilliant core that increases to the center. Brightest of four in HCG 42 with two additional fainter galaxies noted in the group (PGC 852084 and PGC 852825). HCG 42C = MCG -03-26-006 is the closest member at 1.25' NW, barely off the edge of the halo.

Notes by Steve Gottlieb