William Herschel discovered NGC 3485 = H II-100 = h804 = 3309 on 8 Apr 1784 (sweep 187) and noted "F, pL r." JH made three observations at Slough and one at the Cape of Good Hope.

Bindon Stoney, observing on 9 Apr 1852 at Birr Castle "suspected a dark curved passage sp centre." Also on 15 Mar 1855, R.J. Mitchell "suspect[ed] a knot in p and one in f edge. Query, a ring with a Nucl in centre?"

400/500mm - 17.5" (4/18/87): fairly faint, moderately large, fairly diffuse, oval slightly elongated WSW-ENE, faint stellar nucleus. A mag 12 star is 1.7' W of center. Possible member of the Leo group.

Notes by Steve Gottlieb