William Herschel discovered NGC 3506 = H III-22 = h811 on 11 Mar 1784 (sweep 164) and recorded "vF, vS. 240x made it considerably larger, but I saw it well enough with the common power not to doubt of the reality." His position matches UGC 6120. John Herschel made three additional observations. On 18 Jan 1828 (sweep 120) he wrote, "F; S; R; vgvlbM."

The RA in the RNGC is 1.0 minute too large and the galaxy was misplotted in the first printing of Uranometria 2000 Atlas. Also see notes for NGC 3504.

400/500mm - 17.5" (4/22/95): fairly faint, round, 1.0' diameter. Just a weak central brightening with no distinct core or nucleus. Preceded by a trio of mag 13.5 stars within 4'.

17.5" (3/28/87): fairly faint, fairly small, roundish, slightly brighter core. A triangle of mag 13 stars is just west.

Notes by Steve Gottlieb