Albert Marth discovered NGC 840 = m 55 on 2 Sep 1864 with Lassell's 48" on Malta and logged "eF, vS". His position matches UGC 1664 = PGC 8293.
400/500mm - 17.5" (12/18/89): very faint, small, slightly elongated WSW-ENE, low almost even surface brightness.
Notes by Steve Gottlieb