William Herschel discovered NGC 586 = H III-431 = h130 = Sw. III-6 on 10 Sep 1785 (sweep 435) along with NGC 584. See description under NGC 584. John Herschel made a single observation on 8 Jan 1831 (sweep 318), "vF; R; 15 arcsec".

R.J. Mitchell observed NGC 586 with the 72" on 28 and 29 Nov 1856. JH entered the Birr Castle observations as GC 343 = R[osse]. nova. In compiling the 1880 Rosse Catalogue, though, Dreyer noted the equivalence with h130 = III 431. Lewis Swift apparently thought he discovered this object on 30 Nov 1885, though his position for Sw. III-6 was 19 seconds of time too far east. His description stated "south-following GC 363 [NGC 615], but this must be a typo.

400/500mm - 17.5" (8/2/86): fairly faint, fairly small, diffuse, very weak concentration. Located 4.5' SE of NGC 584.

600/800mm - 24" (12/28/16): at 200x and 375x; moderately bright and large, very elongated 5:2 N-S, 1.0'x0.4', small bright core. Forms a pair with much brighter NGC 584 4.3' NW.

Notes by Steve Gottlieb