William Herschel discovered NGC 3512 = H II-366 = h815, along with NGC 3504, on 11 Apr 1785 (sweep 396) and noted "pF, pL, goes into the field with NGC 3504]." He made an offset error as his position is southeast of NGC 3504, instead of northeast. John Herschel measured an accurate position, though he thought it was a new object. He incorrectly equated h815 with H. II-366 in the General Catalogue.

200/250mm - 8" (4/24/82): faint, small, round. Forms a pair with NGC 3504 12' SW.

400/500mm - 17.5" (3/25/95): moderately bright, fairly small, 1.2' diameter, round, weak concentration with an irregular surface brightness. Second of trio with NGC 3504 12' WSW and NGC 3515 14' NNE. Surrounded by three mag 12-13 stars 2.9' N, 3.7' E and 2.1' SW.

Notes by Steve Gottlieb