William Herschel discovered NGC 5239 = H III-101 = h1646 on 13 Apr 1784 (sweep 191) and recorded "eF, pL, R, easily resolvable. I can almost see the stars of it." JH made two observations and his position on sweep 250 is accurate.

400/500mm - 17.5" (5/27/95): very faint, 1.0' diameter. Appears as a very low surface brightness glow with no concentration. Forms the west vertex of a right triangle with two mag 12-13 stars 4.1' E and 5.0' SE.

Notes by Steve Gottlieb