Édouard Stephan discovered NGC 5646 = St XI-25 on 29 Apr 1881. His micrometric position matches UGC 9312. William and John Herschel, both of whom observed nearby NGC 5656, missed this galaxy.

400/500mm - 17.5" (6/20/98): very faint, small. With extended viewing, elongated 3:1 WSW-ENE, 1.0'x0.3', only a weak concentration. Requires averted to see full extensions well. The major axis is collinear with a mag 10 star 2.0' following. Located 13' NW of NGC 5656.

Notes by Steve Gottlieb