William Herschel discovered NGC 4531 = H II-175 = h1333 on 17 Apr 1784 (sweep 199)and noted "pF, L." JH made two observations and recorded (sweep 339) "pF; pL; R; vgbM; 80"."

400/500mm - 17.5" (4/25/87): moderately bright, moderately large, slightly elongated NW-SE, diffuse, broad concentration. Located 37' W of M90.

Notes by Steve Gottlieb