Andrew Common discovered NGC 3865 in 1880 with his 36-inch reflector and reported "F, pL, dif, another sf [NGC 3866] not so L". Common's RA (single position) was 20 seconds of RA too large . Leavenworth probably found this galaxy again in 1886 and reported it as new in list II-449 (later NGC 3854), though his RA was 28 seconds too small, as well as 9' too far south. In 1921, it was reported again as a possible new nebula at the Helwan Observatory with an interesting description: "F, pS, double nebula [probably an a bright section of a spiral arm] separation 20" in p.a. 40. ? = NGC 3865" MCG misidentifies this galaxy as NGC 3858. See Corwin's notes for NGC 3854.

400/500mm - 17.5" (4/15/93): moderately bright, moderately large, elongated 3:2 SW-NE, very small brighter core appears offset from the geometric center. Located 4.5' SE of mag 9 SAO 138385. Forms a pair (identical redshift) with NGC 3866 7' SSE. Probably one of the brightest members of the large USGC S171 group that includes NGC 3730, 3771 and 3791.

Notes by Steve Gottlieb