Otto Struve found NGC 3609 on 18 Mar 1869 with the 15-inch Merz refractor at Pulkovo Observatory while searching for Comet Winnecke (7P/Pons-Winnecke). He discovered this galaxy (UGC 6310) just 2 nights earlier so it also carries the designation NGC 3612. Modern sources mistakenly identify UGC 6321 as NGC 3612. See NGC 3612 for the story.

400/500mm - 17.5" (4/22/95): faint, moderately large, round, 1.2' diameter. Weak concentration to a slightly brighter core. A mag 14 star is just off the south edge 50" from center and a second mag 14 star is 1.8' NW. A brighter mag 11 star lies 3.3' NE. Forms a pair with UGC 6321 (misidentified as NGC 3612 in modern sources) 5.4' E. UGC 6321 appeared extremely faint, small, round, 20" diameter, low surface brightness. A mag 11 star lies 3.9' NW.

Notes by Steve Gottlieb