Herschel discovered NGC 1750 in 1785. 78 years later d'Arrest observed a nearby cluster, which was catalogued as NGC 1746. It is likely that both observed the same cluster, and simply recorded different positions; but there are differing interpretations -- (1) that NGC 1750 is only the southeastern portion of NGC 1746, or (2) that the two are the same cluster, and should have the same designation. Given Herschel's earlier observation, if (2) is correct both should be called NGC 1750; but common usage is to call them NGC 1746, which is backward from their order of discovery. There is also another cluster, NGC 1758, just to the northeast of NGC 1746/1750, but is physically unrelated to them (being about 500 light years more distant), and just happens to be in nearly the same direction.

NGC 1758 is closely aligned with NGC 1746 and 1750 in the sky, but is not physically connected with them, being about 500 light years more distant. See NGC 1750 for a view of the region containing the clusters, and a "map" of their relative positions.

Note that Dunlop's object #231 is listed as NGC 1760, but is also listed as possibly being an observation of NGC 1761. This is due to his reductions (the mathematical conversion of observations to reliable positions in the sky) being poor at best, and exactly what object one of his observations represents often being a mystery. Where (John) Herschel was able to find and verify the existence of an object in Dunlop's list, Dunlop is generally credited with the discovery. Where Herschel could not find Dunlop's object, or was uncertain about whether he had, Herschel is generally credited with the discovery. In this case, Herschel (or Dreyer) decided that the emission nebula (NGC 1760) was the more likely object listed as Dunlop's #231; but since the nearby open cluster extends over some distance, it is possible that Dunlop's observation referred to either or both objects, hence the confusing attribution.

The second IC states "Not found by Howe, is = 1794; see note in NGC". So the identity of the two listings has been known for over a century.