John Herschel discovered NGC 5090 = h3487 on 3 Jun 1834 and recorded "B; pL; R; 60"." His position (measured on two nights) is accurate. Brightest in a group east of the Centaurus cluster.

300/350mm - 13.1" (2/19/04 - Costa Rica): moderately bright, moderately large, slightly elongated E-W, 1.6'x1.3', broad concentration. Forms a close, interesting pair with NGC 5091 1.4' SE of center. NGC 5082 lies 6' W. Located 1° SW of Centaurus A and 4.8' SW of mag 4.8 HD 115988.

400/500mm - 17.5" (4/7/89): fairly faint, moderately large, slightly elongated, even surface brightness. Located 4.8' SSW of mag 6.7 SAO 224083.

17.5" (2/28/87): very faint, fairly small, slightly elongated, low even surface brightness. Located south of a mag 7 star.

Notes by Steve Gottlieb