Herschel discovered the object without recording a visual description. However, he noted the nebula "precedes NGC 507 by about 10 seconds and is half a field to the south of it". NGC 504 was later also independently discovered by Heinrich d'Arrest, using an 11" reflecting telescope in Copenhagen and assuming the object was new. This led to Herschel cataloguing the two observations separately as GC 291 and GC 292.[6] The objects were later combined by John Louis Emil Dreyer with the creation of the New General Catalogue, in which the galaxy was described as "very faint, small".[5]
^ abAn object's distance from Earth can be determined using Hubble's law: v=Ho is Hubble's constant (70±5 (km/s)/Mpc). The relative uncertainty Δd/d divided by the distance is equal to the sum of the relative uncertainties of the velocity and v=Ho