William Herschel discovered NGC 4904 = H II-517 on 1 Jan 1786 (sweep 507) and noted "pB, S, R, bM." A few minutes later he commented in his logbook "twilight pretty strong." His position is 2' southwest of UGC 8121.

400/500mm - 17.5" (5/22/93): moderately bright, elongated 3:2 NW-SE, 1.5'x1.0', brighter bar along major axis, very small brighter core, slightly mottled. A mag 12 star is 1.8' NNW and a mag 14 star 2.2' WSW. On the POSS a very faint outer halo is elongated roughly N-S.

Notes by Steve Gottlieb