William Herschel discovered NGC 5331 = H III-929 = h1687 on 13 May 1793 (sweep 1044) and logged "vF, S, E in meridian." JH made an interesting observation on sweep 144: "A very insignificant cluster of vS scattered stars; or a S[mall] resolved neb." The position here is on the brighter component of the double system.

400/500mm - 17.5" (5/11/96): this double system was resolved with the brighter component (VV 253b) at the north end. VV 253b is fairly faint, fairly small and slightly elongated. Attached at the south end is a low surface glow (VV 253a). The pair requires attention as there is less than 30" separation between centers. NGC 5329 lies 14' N.

900/1200mm - 48" (5/12/18): at 488x and 610x; NGC 5331 is an interacting pair at 25" separation N-S. The southern component (VV 253a) appeared moderately bright and large, elongated NW-SE but with an irregular outline. Contains a brighter elongated core with a faint stellar nucleus. The galaxy thins on the southeast end with a faint extension or tail, creating an asymmetric appearance. The northern galaxy (VV 253b) appeared fairly bright or bright, moderately large, oval 2:1 SW-NE, irregular outline. Contains a high surface brightness elongated core with a stellar nucleus.

CGCG 017-081, situated 1.3' W of the pair, appeared fairly faint, small, round, 15" diameter, a 17th mag star is 15" WSW. A 16th magnitude star lies midway between the CGCG and the NGC pair.

48" (5/4/16): at 697x; NGC 5531 is a fascinating interacting pair (25" between centers) with a third component (CGCG 017-081) 1.3' W. The northern component (VV 253b = PGC 49266) is fairly bright, moderately large, elongated 2:1 or 5:2 SW-NE, 30"x12", sharply concentrated with a prominent, elongated core and bright stellar nucleus. The surface brightness of the halo is irregular with a hint of spiral structure.

The southern galaxy (highly disrupted on the SDSS with a tidal plume to the WNW) is fairly bright, fairly large, elongated 3:1 NW-SE, broad concentration but no well defined zones. The surface brightness, though, is irregular or mottled and the galaxy appears dusty. More unusual is the shape; the galaxy tapers at the southeast east and the northwest end bends or twists towards the northern spiral, creating a kidney-bean outline.

CGCG 017-081, 1.3' W, appeared fairly faint, small, round, 15" diameter, nearly even surface brightness. A mag 16.5 star is just 14" WSW of center. A mag 16 star sits midway between this galaxy and the NGC 5331 pair.

Notes by Steve Gottlieb