Heinrich d'Arrest discovered NGC 4091, along with NGC 4089, on 2 May 1864 and described a double nebula separated by 3 sec in RA. His mean position from 4 nights matches UGC 7083 = PGC 38308.

400/500mm - 17.5" (5/14/88): faint, very small, elongated SW-NE. A mag 13.5 star is 1.0' S. Forms a very close pair with NGC 4089 37" W of center and the second of six in the field within the NGC 4065 cluster.

Notes by Steve Gottlieb