William Herschel discovered NGC 2539 = H VII-11 = h3114 on 31 Jan 1785 (sweep 363) and called it "a cluster of stars, coarsely scattered, but considerably rich, above 20' diam." JH, observing from the Cape of Good Hope, recorded "a large, extended, rich cluster. Fills field; stars 12th mag approx. A bright star (6th mag) S.f."

300/350mm - 13.1" (2/25/84): about 85 stars in a 20' diameter. Fairly rich with uniform magnitudes. A brighter mag 10/11 pair at 21" is on the north side. Located about 10' NW of 19 Puppis (V = 4.7).

400/500mm - 18" (3/2/08): this cluster is situated 10' NW of 4.7-magnitude 19 Pup. Roughly 125 stars are spread out over a 20' region. At the NW end is a roughly equal mag pair, an 11" pair is on the east side and a brighter mag 10/11 pair at 20" is on the NE side.

Notes by Steve Gottlieb