George Johnstone Stoney, Lord Rosse's assistant, discovered NGC 4402 = Au 30 on 13 Apr 1849 and labeled it Eta on the diagram of the central core of the Virgo cluster. He also noted "Eta hollow in the middle [dust lane], probably a ring seen obliquely, faint star north of its middle, seen best with the single lens."

Arthur Auwers independently discovered NGC 4402 on 5 Mar 1862 with the 6.2-inch Fraunhofer heliometer at the Königsberg Observatory and recorded "faint, gradually brighter in the middle, much elongated in the parallel [east-west], 3' long and 1.5' broad." Auwers is credited with the discovery in the GC and NGC as no positions or offsets were measured at Birr Castle.

300/350mm - 13.1" (5/14/83): faint, fairly large, even surface brightness.

400/500mm - 17.5" (4/25/87): fairly faint, fairly large, very elongated 3:1 E-W, fairly even surface brightness. Located 10' N of M86 in core of the Virgo cluster.

600/800mm - 24" (4/28/14): moderately bright, fairly large, very elongated 7:2 E-W, 2.1'x0.6'. Very mottled, patchy appearance implying a dusty equatorial plane and HII regions, though individual knots were not resolved. M86 is 10' N.

Notes by Steve Gottlieb