Harold Corwin

Malcolm has pointed out that this number and IC 4051 may have been switched by most observers and in most cataloguers. Only Bigourdan and Vorontsov-Velyaminov in MCG put the NGC number on the brighter, larger, south-southeastern object. d'Arrest's position, copied correctly into the NGC, actually falls a bit closer to the smaller, fainter north-northwestern galaxy of the pair.

And the IC position, adopted from Kobold's micrometric observation, lands almost exactly on the brighter object because he was apparently the first observer to put the NGC identification on the fainter object. Bigourdan did the opposite, but Dreyer apparently went with Kobold's position simply because, as published, it is has more precision. Bigourdan is still credited as a co-discoverer of the IC galaxy, though.

I suspect that Dreyer did not make much of a fuss about the discrepancy between Kobold and Bigourdan because he was distracted by an identification problem involving H III 363 -- John Herschel incorrectly put this number on h 1510 = NGC 4894 (which see). Again, Malcolm and I think that William Herschel, like d'Arrest, must have seen NGC 4908, the brighter of the two galaxies. So, Dreyer's identification of William Herschel's object as IC 4051 is as misleading as the NGC and IC positions.

In any event, because of Kobold's assumption that the NGC position is for the fainter galaxy, just about everyone has the identifications reversed. This probably includes Milton Humason who found a supernova near "IC 4051" in 1950. Unfortunately, Humason does not give a position or a finding chart for the SN and galaxy in his PASP note, but I am pretty sure that it is the brighter, southern object.

All this stands on d'Arrest's having actually seen the brighter galaxy. If he actually saw the fainter -- and it is only a few tenths of a magnitude fainter -- then the NGC and IC have exactly the correct identifications. And so does everyone except Bigourdan and MCG.

But it is much more likely that d'A saw the brighter object.

― NGC Notes by Harold Corwin

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