William Herschel discovered NGC 3640 = H II-33 = h864 on 23 Feb 1784 (sweep 158) and logged "a nebula like the former [pB, bM, vS], but a good deal larger and more regular; almost cometic." His position is poor (not uncommon in early sweeps) -- 50 sec of RA too large -- but there are no other bright nearby galaxies. JH logged "B; R; psbM; 30"." and measured an accurate position.

200/250mm - 8" (4/24/82): bright, moderately large, bright core, slightly elongated.

400/500mm - 17.5" (2/8/91): bright, moderately large, small very bright core, oval halo 3:2 E-W, 15" substellar mottled nucleus. A mag 14 star is 2.3' N. Brightest in a group and forms a close pair with NGC 3641 2.5' SSE.

600/800mm - 24" (5/20/20): at 375x; very bright, fairly large, slightly elongated, 2' diameter, strong concentration with an intense oval core. The nucleus is small, round and very bright. Forms a very close pair with NGC 3641 2.4' SSE.

Notes by Steve Gottlieb