William Herschel discovered NGC 560 = H III-441 on 1 Oct 1785 (sweep 448) and logged "vF, vS, iE." Édouard Stephan independently found the galaxy (St VIII-1, second list) on 21 Nov 1878 with the 31" reflector at the Marseille Observatory. He noted his object was probably the same as H. III-411 and St VIII-2, second list, was the probably the same as H. III-442 (later NGC 564). Harold Corwin found that Stephane Javelle's J. 1-58 (later IC 117) was found by Corwin to be a duplicate observation, due to an error in identifying the offset star. So, NGC 558 = IC 117. See Corwin's write-up on this error.

300/350mm - 13.1" (9/22/84): fairly faint, small, elongated ~N-S, bright core. Located 5' WSW of NGC 564.

400/500mm - 17.5" (1/1/92): fairly faint, fairly small, elongated 2:1 N-S, well-defined very small bright core, faint narrow extensions. In a trio with NGC 558 4' SSW and NGC 564 6' ENE within in AGC 194.

600/800mm - 24" (9/23/17): at 375x; fairly faint to moderately bright, very elongated at least 3:1 N-S, ~50"x15", slightly brighter core, small bright nucleus. Middle of 3 with NGC 558 4' SW and NGC 564 6' ENE. Also IC 120 is 12' E and IC 119 is 11' SE.

Notes by Steve Gottlieb