George Johnstone Stoney, Lord Rosse's assistant, discovered NGC 2458 = Big. 29 on 20 Feb 1851. The number was assigned to one of a "Great many knots, reckoned 10 nearly in a line p f." This was the only observation made at Birr Castle and no positions were measured or even a rough sketch produced. John Herschel added 8 additional entries in the GC, as h469 (later NGC 2463) and H III-836 = h470 (later NGC 2469) were previously discovered, but was unable to provide specific coordinates for these 8 objects. Harold Corwin notes that Stoney likely observed only the 6 brightest galaxies in this region, so 4 of his objects are probably single stars or asterisms.

Dreyer followed Bigourdan's observation on 9 Mar 1886 in assigning positions and descriptions ("vF,*12 close"). Bigourdan's position is 23 sec of RA west of MCG +10-12-016 = PGC 22220 and this galaxy has a mag 12-13 star just 35" SW, matching his description. RNGC, PGC and LEDA (as well as Megastar, etc) misidentify this galaxy as NGC 2461. NED does not assign a NGC designation to PGC 22220. As this is one of the brighter galaxies, it's reasonable to equate NGC 2458 with= PGC 22220.

400/500mm - 17.5" (1/19/91): not found.

600/800mm - 24" (1/25/14): faint, very small, round, 10" diameter, quasi-stellar nucleus. A mag 13.5 star lies 35" SW. Located 4.8' ENE of a mag 10.5 star and second in a string of 6 faint galaxies (several of which have identification problems). This galaxy is identified as NGC 2461 in many sources. PGC 22191 lies 2.8' NW.

Notes by Steve Gottlieb