R.J. Mitchell, Lord Rosse's assistant, discovered NGC 3165 on 30 Jan 1856. While observing NGC 3166 and 3169 he noted "about 5' sp 684 NGC 3166] is a vvF ray extending N-S." The NGC RA is 15 sec too small. Probably based on the poor NGC position, NGC 3165 was included as #212 in a catalog of new nebulae and clusters found on photographs taken by Keeler between 1898-1900 and published in the 1908 Publications of Lick Observatory, Vol VIII.

400/500mm - 17.5" (3/23/85): very faint, elongated 2:1 N-S. Forms the western vertex of a triangle with two mag 12.5 stars 1.9' SE and 1.7' NE. First and faintest of three located 4.6' SW of NGC 3166 and 12' SW of NGC 3169.

Notes by Steve Gottlieb