William Herschel discovered NGC 3940 = H III-380 = h1004 on 26 Apr 1785 (sweep 402) and noted "F, S." His position is 10 sec of RA following UGC 6852. WH found NGC 3940 again on 27 Dec 1786 (sweep 671) and noted "suspected; but doubtful; probably 2 vF and very close stars." On this sweep, CH's reduction is 3' too far south-southwest, though he didn't equate it with his earlier observation.

400/500mm - 17.5" (4/7/89): fairly faint, small, slightly elongated WNW-ESE, small bright core, stellar nucleus. A mag 11 star is 2.4' SE. Member of the NGC 3937 group with NGC 3946 8.2' ENE and NGC 3929 12' W.

600/800mm - 24" (5/20/20): at 225x and 375x; fairly faint, fairly small, round, slightly brighter core that is sharply concentrated with a very small bright nucleus, ~40" diameter with suggestions of a larger very low surface brightness halo.

Notes by Steve Gottlieb