Heinrich d'Arrest discovered NGC 4584 on 21 Apr 1862 with the 11-inch refractor at Copenhagen. His measurements on 3 nights matches UGC 7803 and he noted a mag 15 star (called mag 18) that follows by 16 seconds of time.

400/500mm - 18" (4/10/04): fairly faint, fairly small, round, 40" diameter, weak concentration.

Notes by Steve Gottlieb