William Herschel discovered NGC 3504 = H I-88 = h810, along with NGC 3512, on 11 Apr 1785 (sweep 396) and noted "cB, cL, iR, bM." John Herschel made a total of 7 observations. R.J. Mitchell, observing at Birr Castle on 22 Feb 1857, recorded "mE, B nucl, arms faint, patchy,suspect dark space all around the nucleus." A month later he described "pL, Nucl vB and has a sensible disc, arms vF and patchy. I think I see a knot or patch in np end of neb."

The RA in the RNGC is 1.0 minute too large and the galaxy is misplotted on the first version of Uranometria 2000 (later fixed). Also see NGC 3506.

400/500mm - 17.5" (3/25/95): bright, large, elongated 2:1 NNW-SSE, 2.5'x1.2'. The [inner] halo has a fairly high irregular surface brightness. Sharp concentration with a very small well-defined core dominating. The bright core appears offset to the south side with the halo more extensive to the north. Two mag 14 stars lie 1.7' NNW (45" separation). First of three with NGC 3512 12' ENE and NGC 3515 24' NE.

Notes by Steve Gottlieb