NGC/IC Project Restoration Effort

===== NGC 980 and NGC 982. William Herschel found these two nebulae, but did not measure individual positions; his position is "between them." Thus, it is John Herschel's positions that are used in the GC and NGC. Unfortunately, JH did not carry over into the GC his uncertainty in the position of H III 572 = h 235; this is noted in his 1833 catalogue (RA and NPD): "02 24 40.5:, 49 55 25:". The other nebula, H III 573 = h 235 carries no such uncertainty symbols: "02 24 44.8, 49 52 39." If this latter position is precessed to 1950, it agrees closely with those measured by Bigourdan and by Dressel and Condon for "NGC 980." Dressel and Condon, of course, simply copied the designation from UGC. Bigourdan gives no reason for his identifications, simply noting that "NGC 982" is fainter than "NGC 980." The MCG, however, calls this southeastern object "NGC 982," apparently preferring to believe that the NGC declination is incorrect rather than the right ascension. Who's right? Let's look back at John Herschel's observations since that is where the incorrect position comes from. If we precess his uncertain position for the western object, we find that the RA but not the declination agrees with that from the modern observations. So, the two galaxies are oriented northwest- southeast on the sky, but the NGC positions (from Sir John) say southwest- northeast. Indeed, the GC and NGC descriptions state this orientation explicitly. However, Dreyer has a note in the NGC repeating part of Sir John's original description for h 235: "Dist. 3 arcmin; pos from the next one = 337.0 deg," and adding, "Is the p one perhaps the most northern? H says nothing about their relative position; not observed by d'A." John Herschel's note about the position angle between the two being 337 deg is the vital clue here, since it suggests that the nw/se orientation is correct. Let's now take the position of h 236 as correct -- as indeed it is within the known statistical errors of Sir John's observations (about 2 arcmin). Now, assume that Sir John measured the position of h 235 with respect to h 236, perhaps by measuring the distance and position angle that he quotes. This would then imply that he made an error in calculating the offset in declination. If this is true, then changing the sign of the declination offset (2 arcmin 46 arcsec) would put the declination exactly on the true declination: +40 42.5 for 1950 (NPD = 49 49 53 for 1830). So, here is another case where the position for a nebula was measured with respect to another nearby nebula, which in turn was referred to the "fundamental" reference system (see the note on NGC 2424 and 2427 for another instance of this). So, I think that the declination of NGC 980 is out by 5.5 arcmin, that the UGC identifications are switched, and that the MCG got them right. Another minor mystery: in the GC, JH has the distance as "210 arcsec" rather than "3 arcmin". This makes his observation closer to the true distance on the sky. I suspect that it comes from his original observing records -- but why didn't he use it in his 1833 list?

===== NGC 980 17.5" (11/27/92): faint, fairly small, elongated 5:2 WNW-ESE, small bright core, similar appearance but slightly fainter by 0.5 mag than NGC 982 3.5' S. Identifications of NGC 980/NGC 982 reversed in the RNGC, UGC, CGCG.