Heinrich d'Arrest discovered NGC 5259 on 27 Apr 1865 with an 11" refractor at Copenhagen and confirmed the observation the next night. His mean position is within the halo of CGCG 161-105 = PGC 48292 and he noted the mag 6.2 star (called mag 8-9) ~12' east and 1.5' north.

The RNGC coded description reads "E, R, BM, *CLOSE NPR", but the "star close north preceding" is a compact meging companion.

400/500mm - 17.5" (6/12/99): very faint, very small, round, 25" diameter, very weak concentration. Two mag 14.5-15 stars lie 2' NW. Located 11' W of mag 6.2 SAO 63676. A very faint, compact companion on the NW edge was not noticed.

600/800mm - 24" (5/20/17): at 200x; faint, small, round, 25"-30" diameter, very small brighter nucleus. Two 15th magnitude stars lie 2' NW. Located 11' W of mag 6.2 HD 119035. Using 375x an extremely faint and small merging companion (Holm 533B = NGC 5259 NED1) was often visible with averted vision at the northwest edge of the halo. It appeared as a quasi-stellar knot, at most 5" diameter and with concentration could be held perhaps 1/2 the time. The separation of this merging pair is 19" (between nuclei) with a projected distance of 77,500 l.y.

Notes by Steve Gottlieb