Lewis Swift discovered NGC 3588 = Sw. I-12 on 26 Apr 1883 and recorded "cS; vF; follows Delta Leonis 4 sec. Easily overlooked." His position, 8' south of Delta Leonis, matches UGC 6264. He specifically looked at Delta Leonis, hoping to find a nebula, hidden in the glare of a bright star. This was his first discovery while still adjusting and testing his new 16-inch Clark refractor.

400/500mm - 18" (5/31/03): very faint, very small, round, 0.4' diameter. Weak, even concentration to center. Located just 8' S of mag 2.6 Delta Leonis! (Zosma). Not difficult at 320x with Delta just outside of field.

Notes by Steve Gottlieb