William Herschel discovered NGC 5739 = H I-171 = h1873 on 18 Mar 1787 (sweep 718) and noted "pB, R, S, lbM, r." His position was 3' north and 9 sec of RA west of UGC 9486. Less than a month later on 9 Apr 1787 (sweep 725), he logged "cB, S, mbM, r." JH noted that several faint stars were near and measured a good position.

200/250mm - 8" (4/24/82): faint, small, round, bright core.

400/500mm - 17.5" (6/27/98): fairly faint, fairly small, slightly elongated SW-NE, 1.2'x1.0', well concentrated with a small bright core. A mag 14 star is just off the northeast end 0.8' from center and three additional nearby mag 14-15 stars form a parallelogram with this star.

Notes by Steve Gottlieb