Édouard Stephan discovered NGC 923 = St X-11 on 30 Oct 1878 with the 31" reflector at the Marseille Observatory and recorded "vF, S, R, weak concentration". His position matches UGC 1915 = PGC 9355.

In March of 2020, Yann Pothier suggested the original discovery was made by Dreyer on 6 Nov 1874, though he assumed his observation applied to H. III-570 = NGC 898. His description, which reads "pB (at least not vF), S, lE npp sff. A * in Pos. 27.3°, Dist. 145.5".", does not apply to NGC 898, but NGC 923 instead, which is located 4.2 minutes of time east of NGC 898.

Wolfgang Steinicke added the following comments: "The reason why Dreyer missed III 570 NGC 898) on 6 Nov. 1874 is not due to an incorrect setting of the 72-inch. This is shown by correct data given for the other objects in that night (all observed before GC 533 NGC 898]): GC 5036 (NGC 7794), GC 82 (NGC 169+IC 1559) and GC 272/78/89 (NGC 483/95/99). Dreyer simply had no coordinates. The main source of the Birr Castle astronomers were JH's catalogues (h, GC). Unfortunately, JH could not find III 570 (and III 571 = NGC 910) in his sweeps, though both objects were in his working lists, prepared by CH from her zone catalogue. Thus young Dreyer could only use WH's 2nd catalogue, giving relative positions to Beta Persei. Happy to see a "lE" nebula (at the place of NGC 923), he took the first choice: III 570 NGC 898), though not at WH's place. For Dreyer derived no position for himself, he used WH's in his catalogues [and therefore later entered Stephan's observation to the NGC as a new object]."

300/350mm - 13.1" (11/5/83): very faint, very small. Located just 2.4' SSW of mag 9 SAO 38041, which interferes with viewing. Member of AGC 347.

400/500mm - 18" (11/26/03): faint or fairly faint, small, round, 25" diameter, weak concentration. Located 2.4' SSW of a mag 9 star. Second of three on a line with fainter MCG +07-06-023 1.8' NNE and MCG +07-06-21 2.8' SSW in AGC 347.

600/800mm - 24" (11/23/19): at 375x; fairly faint (relatively bright member of AGC 347), fairly small, elongated 3:2 ~E-W, brighter core, 0.6'x0.4'. Collinear with CGCG 539-029 3' SSW and CGCG 539-031 1.8' NNE. A mag 8.7 star (HD 15163) is 2.4' NE.

Notes by Steve Gottlieb