NGC/IC Project Restoration Effort

===== NGC 3924 = NGC 3922. "Both" objects were discovered by William Herschel, but the positions that he gave them were rather discordant. He found N3922 = H III 716 on 9 March 1788, and placed it at 11 48.5, +50 29. N3924 = H II 825 was placed at 11 51.1, +50 33 (1950) by its discovery observation on 8 March 1789. But the next year (17 March 1790), Herschel redetermined its position and found 11 48.9, +50 28. Within Herschel's usual errors, this position is identical with that for III 716. Dreyer realized the identity when he was preparing his edition of William Herschel's Scientific Papers which he collected and published in 1912. He also has a brief note about it in MNRAS 73, 37, 1912. I think the NGC positions come from d'Arrest or Tempel, but haven't chased them down yet. Dreyer also has an intriguing note on the pair in the NGC itself: Tempel apparently saw two nebulae here, though d'Arrest picked up only the brightest. The confusion in the current catalogues comes from both CGCG and MCG which identify both numbers differently. There are many faint galaxies in the area (which is right in the plane of the Local Supercluster, and in the heart of the Ursa Major Cloud), but only one with a surface brightness high enough to be picked up easily at the eyepiece. This is the one that Herschel observed at least three times, and can be confidently called "NGC 3922 = NGC 3924." This is MCG +08-22-017 = UGC 6824. Though CGCG and UGC put the number N3924 on UGC 6849 = MCG +08-22-026, this is a low surface brightness galaxy that Herschel probably would not have noticed while sweeping. (Could this be Tempel's second nebula, though? I'll have to check.) Unfortunately, UGC, RNGC, and RC3 copied CGCG's incorrect identification for UGC 6849.

===== NGC 3924 See observing notes for NGC 3922. This number is incorrectly applied to UGC 6849 in the RNGC, UGC, CGCG, RC3!