NGC 584 is an elliptical galaxy in the constellation Cetus. The galaxy was discovered on 10 September 1785 by the German-British astronomer William Herschel. It is about 20 megaparsecs (60 million light-years) distant. NGC 584 belongs to the NGC 584 galaxy group, which also includes the galaxies NGC 596, NGC 600, NGC 615 and NGC 636.

200/250mm - 8" (9/25/81): bright, round, bright core.

400/500mm - 17.5" (8/2/86): very bright, moderately large, oval WSW-ENE, very bright large core. Forms a pair with NGC 586 4.5' SE.

600/800mm - 24" (12/28/16): at 200x and 375x; very bright, large, oval ~3:2 SW-NE, ~2.4'x1.6', sharply concentrated with an intensely bright core that gradually increases to quasi-stellar nucleus. Brightest in a group (LGG 027) with NGC 586 4.3' SE. LEDA 1028168, situated 7' WNW, appeared extremely faint, fairly small, irregularly round, 20" diameter, very low surface brightness.