William Herschel discovered NGC 3591 = H III-529 = h3331 on 27 Mar 1786 (sweep 548) and noted "eF, S." JH recorded "vF; R; 30"; vlbM" and measured an accurate position.

400/500mm - 18" (3/19/04): fairly faint, fairly small, slightly elongated NNW-SSE, 0.9'x0.7'. Contains a very small brighter nucleus, ~10" diameter.

Notes by Steve Gottlieb