William Herschel discovered NGC 5210 = H III-99 = h1629 on 13 Apr 1784 (sweep 191) and recorded "eF, S. It follows a star 7-8 mag 3.1 min in time and 1° 9' more north." On 12 May 1793 (sweep 1042) he reported "pBN with vF chevelure [halo]. S, almost like a faint nebulous star." JH logged "F; S: R; psbM; 15"." and measured an accurate position.

400/500mm - 17.5" (5/27/95): faint, fairly small, round, 1.0' diameter. Contains a fairly bright core with a faint halo with fades into the background. Similar to the NGC 5208/5209 pair that lies ~10' NNW.

600/800mm - 24" (6/1/13): moderately bright, moderately large, round, 0.8' diameter, sharply concentrated with a small bright core that increases to a stellar nucleus. Brightest in a group (WBL 450), along with NGC 5208 and 5209, which lie 10' NNW.

Notes by Steve Gottlieb