William Herschel discovered NGC 1635 = H II-515 = h325 on 1 Jan 1786 (sweep 506) and recorded "F or pB, S, bM." On 23 Nov 1827 (sweep 107), John Herschel logged, "vF; R; has a *9m about 12.5 sec following to the north." At Birr Castle (13 Jan 1863) it appeared "very like a distant globular cluster, just plainly visible."

400/500mm - 17.5" (1/23/93): moderately bright, fairly small, round, 1' diameter, increases to very small prominent core. An easy mag 13 double star at 24" separation is just 1.0' NW. Located 3.5' WSW of a mag 10 star and 7' S of mag 9 SAO 131395.

Notes by Steve Gottlieb