William Herschel discovered NGC 5791 = H III-691 = h1889 on 19 May 1787 (sweep 741) and recorded "cF, stellar, smbM." JH logged "pF; R; bM; 20" and measured a fairly accurate position. JH missed nearby IC 1081.

300/350mm - 13" (6/18/85): moderately bright, dominated by a bright core surrounded by faint extensions roughly NW-SE. A mag 11 star is 4.7' SSE.

400/500mm - 17.5" (6/16/01): moderately bright, oval elongated 2:1 NNW-SSE, 1.5'x0.7'. The faint halo contains a bright core that increases to a quasi-stellar nucleus. Brightest in a group and forms a close pair with IC 1081 2.7' NE. A mag 12 star lies 3' SE. Located 5' NNW of mag 10 SAO 158945. IC 1081 appeared very faint, very elongated NW-SE, 1.2'x0.3', low even surface brightness. Very weakly concentrated.

Notes by Steve Gottlieb