William Herschel discovered NGC 3403 = H II-335 = h767 on 3 Apr 1785 (sweep 390) and noted "pF, cL, iE." On 4 Nov 1831 (sweep 382), John Herschel reported, "pF; L; E; vgbM; 60" l, 40" br."

400/500mm - 17.5" (2/8/91): fairly faint, moderately large, elongated 5:2 WSW-ENE, weakly concentrated. A mag 12.5 star is 3.1' SE of center.

Notes by Steve Gottlieb