Lewis Swift discovered NGC 6420 = Sw. II-56, along with NGC 6419, on 17 Aug 1883 and recorded "eeF; eS; R; ee diff. s[outh] of 2 [with NGC 6419]. His description is not of any real help, but his position is 23 seconds of RA west of CGCG 321-025 (off by 2.2'). Bigourdan measured an accurate position (matching the CGCG) on 6 Sep 1888. See notes for NGC 6419.

400/500mm - 17.5" (6/11/88): very faint, very small, round, bright core. In a compact trio with NGC 6422 1.3' ENE and MCG +11-21-014 1.3' NNE. Located 6.3' S of NGC 6419.

600/800mm - 24" (6/16/20): at 260x; fairly faint, fairly small, slightly elongated SW-NE, 25"x20", small bright nucleus. In a group with brighter NGC 6422 1.4' ENE.

Notes by Steve Gottlieb