John Herschel discovered NGC 504 = h107 = Au 12 on 22 Nov 1827. No visual description was published but he noted it "precedes III.159 [NGC 507] by about 10 sec, and is half a field to the south of it." Heinrich d'Arrest independently discovered this object on 8 Oct 1861 with the 11-inch Fraunhofer refractor in Copenhagen. His discovery was included in Auwers 1862 catalogue of new nebulae with a total of 5 observations in d'Arrest's 1867 "Siderum Nebulosorum". JH catalogued the two observations separately as GC 291 and 292, but Dreyer combined them to NGC 504, assigning credit to d'Arrest.

300/350mm - 13.1" (8/8/86): faint, small, very elongated 3:1 SW-NE, small bright core. First of three with NGC 507 4' NNE and NGC 508 5.3' NNE. Also NGC 494 lies 7.2' WSW.

600/800mm - 24" (10/4/13): fairly bright, fairly small, elongated 5:2 SW-NE, ~40"x16", well-concentrated with a very bright elongated nucleus and faint extensions. Located 4' SW of NGC 507 in the core of the NGC 507 Group. IC 1687 is 4.7' NNW, NGC 508 5.2' NE, NGC 494 7' WSW.

Notes by Steve Gottlieb