William Herschel discovered NGC 6522 = H I-49 = h3720, along with NGC 6528, on 24 Jun 1784 (sweep 232) and recorded "B, pL, bM, r." John Herschel logged this cluster twice, first recording on 3 Aug 1834: "Globular cluster; pB; S; R; 80: resolved into stars 16m." On a later sweep he logged "GC; B; R; gvmbM; in a nebuloid portion of the milky way; resolved; stars 16...17m."

300/350mm - 13.1" (6/29/84): moderately bright, mottled. A single brighter 13th mag star is on the ENE side. This is the larger and brighter of a pair of globulars with NGC 6528 15' E in Baade's Window.

400/500mm - 17.5" (7/11/99): this globular is the larger and brighter of a fairly faint pair with NGC 6528 in the same field just 16' E. At 220x the halo extended ~2' diameter and contained a very small bright core. A mag 12.5-13 star is embedded in the northeast side. At 280x, the ~25" core appeared offset east of center and the halo was slightly elongated E-W. An unresolved string or bar of stars oriented WNW-ENE (just slightly fainter than the core) appeared to pass through the core . The globular was lively but without distinct resolution. With averted vision the outer haze increased in size to ~3'.

Notes by Steve Gottlieb