Heinrich d'Arrest discovered NGC 4842 on 24 Apr 1865 with the 11-inch refractor at Copenhagen, while observing and measuring NGC 4839. With respect to NGC 4839 his position is 11-12 sec of RA east and 0.4' north. The actual offset is 11.5 sec east and 0.3' south (to the brighter northern component), so he apparently reversed the offset sign in declination. As a result the NGC position is off from d'Arrest's usual accuracy. The two components are listed separately in the MCG.

400/500mm - 17.5" (5/14/94): very faint, very small, very small bright core, possible stellar nucleus. Forms a close pair with NGC 4839 just 2.6' W. At 280x, this galaxy is resolved into a double system with an extremely faint, nearly stellar companion (NGC 4842B) 30" S of center. The close double STF 1699 = 8.6/8.6 at 1.6" separation lies 14.4' E. Member of AGC 1656.

Notes by Steve Gottlieb