Heinrich d'Arrest discovered NGC 5531 on 7 Feb 1862 with the 11-inch refractor at Copenhagen. His position (measured on two nights) matches CGCG 074-155 = PGC 50999.

400/500mm - 17.5" (5/15/99): faint, fairly small, round, 0.8' diameter, low even surface brightness. Located near midpoint of NGC 5531 5.2' SSE and a mag 9.5 star 5' NW. An attached companion on the south side was not noticed.

600/800mm - 24" (6/15/15): fairly faint, fairly small, round, 30" diameter. Forms a merged pair with SDSS J141643.57+105252.4 = LEDA 4409321 barely within the halo, just 16" SSE of center. At 375x (6mm ZAO) this small companion appeared as a faint, very small extension at the south-southeast edge of the halo.

Notes by Steve Gottlieb