William Herschel discovered NGC 2309 = H VI-18 = h417 on 4 Mar 1785 (sweep 377) and logged "a cluster of considerably compressed small stars, pretty rich, 8 or 9' diameter, irr figure. With a smaller aperture it would probably appear nebulous." On 13 Mar 1828, John Herschel described "a cluster, not v rich; 4' diam' irreg fig' st 12...13m."

400/500mm - 17.5" (1/1/92): three dozen stars mag 11-15, fairly rich, compact, 4' diameter. Most stars are located within two streams. The brighter stars in the southern stream are oriented E-W. A fainter star lane to north is oriented NW-SE. At the NW end it hooks NE to mag 9 SAO 133914 about 4' N of the cluster's center. Includes several close pairs with two pairs near the center and a double star 11/14 at 7" separation at the west end.

Notes by Steve Gottlieb