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The correct identify of an NGC entry is important for several reasons. First, the historical
integrity of the NGC should be preserved. Credit should be given to the early visual observer for
the object which was actually discovered. In the case of duplicate entries or erroneous sightings
such as close double stars, these numbers should be probably identified and not assigned to nearby
Second, the NGC numbering scheme is still the primary identification used by professional astronomers. Erroneous or conflicting numbers should be cleared up for consistency in the literature.
Third, with the recent widespread availability of amateur telescopes in the 16" or larger class, the entry NGC has come within the grasp of the serious amateur. As fainter galaxies in the mag 14- 15 range are observed, correct identifications can be a time consuming and difficult task, especially when major catalogues disagree on their identifications. The recent Uranometria 2000.0 star atlas is a major step forward in this direction, but in often relying on the RNGC as its reference source for NGC entries, it has compounded some of these RNGC errors. For these reasons it is important to bring to light identification problems as they are uncovered so we may have a historically accurate NGC.
I would like to thank Jeff Corder and Jim Lucyk who both presented leads on several of the NGC entries in this list based on their own observations and research. In addition, Malcolm Thomson was of great assistance is providing historical data to confirm many of these identification errors.
NGC 4: This galaxy was discovered by Albert Marth using Lassell’s 48" equatorial at Malta. According to Marth NGC 4 is located 5' N and 10 seconds of RA following NGC 3 which he discovered on the same night. The RNGC identifies NGC 4 with an anonymous galaxy 15' southeast of NGC 3 – clearly an incorrect match.
Interestingly, in Marth's original position, 4.7' NNE of NGC 3, there is an extremely faint galaxy which I was just able to glimpse with my 17.5" at 220x a few arc minutes preceding a brighter star. Harold Corwin gives a precise 2000 position for NGC 4 at 00 07 24.4 +08 22 23.
NGC 846, 847: These two NGC entries come from Stephan and Swift, respectively. Both observers described galaxies with nearly identical coordinates. Stephan's micrometric position exactly matches the single galaxy in the vicinity but Swift's description and close position also pins down the same galaxy. In Astronomische Nachrichten (AN) #2992, Spitaler concluded that NGC 846 = NGC 847 and the Catalogue of Galaxies and Clusters of Galaxies (CGCG) and Uppsala General Catalogue of Galaxies (UGC) concur. Since Stephan first discovered this galaxy first in 1877, his number NGC 846 should apply by historical precedence.
With a 13" f/4.5 Newtonian, I described this galaxy as "fairly faint, weak concentration, almost round, in a rich field. Located 4' NW of mag 9.2 SAO 37855.
The RNGC incorrectly identifies NGC 847 with an extremely compact galaxy (or very close double star) located 6' north of NGC 846.
NGC 1037: Discovered by Lewis Swift and recorded in his list #5 in AN #2763. There is no galaxy near Swift's position of 02 39 58.1 -01 44 02 (2000) and no other nearby galaxies that he recorded during the same evening. Strangely, Swift mentions that GC 581 = N1032 is in the field which is impossible given his position for NGC 1037. Furthermore, there is no galaxy in the field of NGC 1032 either.
The RNGC (also RC3 and PGC) incorrectly identifies N1037 as UGC 2119 = A0235-02 which is located 2 minutes of RA west of Swift's position.
NGC 1062: Discovered by Ralph Copeland at Birr Castle in the N1060 group. The observation of 11 Oct 1873 clearly placed this object 116.8" in PA 97.6 (ESE) of N1061. The galaxy identified in the RNGC and RC3 as N1062 is UGC 2201 which is located over 6' ENE of N1061.
Interestingly, 1.9' ESE of N1061 is an extremely faint star which is probably the object recorded by Copeland. Harold Corwin measured a position of 02 43 24.8 +32 27 42 (2000) for this star.
NGC 1109, 1111: Discovered in a large group of faint galaxies by Marth. Several galaxies in this group have questionable identifications including N1109, N1111, N1112, N1113 and N1117. Marth placed N1111 just 1' south and 4 seconds of RA following N1109. The anonymous galaxy identified as N1111 in the RNGC is located 7' south and 9' east of N1109. This confusion is also related to Marth's poor position for N1109 which 38 seconds of RA and 2' N of the correct place. Javelle later recorded the correct position for this galaxy as IC 1852 and it is listed with this identification in UGC (U02293), MCG (M+02-08-011) and CGCG (Z440-015). Assuming N1109 = IC 1852, then the RNGC has incorrectly identified N1111 based on Marth's offset for N1109.
NGC 1117: Marth entered this object on the same evening as N1109, N1111 and several other faint galaxies in the group. Marth placed N1117 10' south and 8 sec of RA east of N1116. The galaxy identified as N11117 in the RNGC is a triple galaxy located 8' south and 37 sec of RA east of N1116. This galaxy is not identified as N1117 in the UGC (U02337), CGCG (Z440-0222) or MCG (M+02-08-019/020). This may simply be a poor position from Marth as his description does mention "close to a small star" which could refer to a fainter component of this multiple system.
NGC 1330: Discovered by Stephan and place 6' north of N1335, who position and identity is secure. Stephan's micrometric position falls precisely on two mag 15 Hubble Guide Star Catalogue stars. On the POSS, this appears to be a group of at least four stars (there is a very elongated merged image of two or three stars). RNGC incorrectly identifies N1330 with Z541- 014 located 12' south of N1335. UGC does not identify U02762 as N1335 although Stephan's position is an exact match.
NGC 1717: Discovered by the Birr Castle observers in the field of N1719. Recorded only the single observation of 1849, Jan 15 as one of three "vF nebulae". This object was not found on three subsequent observations of the field and the comment was added that two of these three are probably N1713 and N1719 while the third "nebula" could possibly be a mag 13-14 star recorded by d'Arrest 4.7 sec preceding and 80" north of N1719. The RNGC correctly identifies N1717 as nonexistent but states it is identical to N1719. According to Harold Corwin and the UGC notes, N1717 refers to a single star 1.7' NW of N1719 at 04 59 30.0 -00 14 15 (2000). The MCG incorrectly identifies N1719 as M+00-13-060.
NGC 2242: Lewis Swift discovered this nebula with a 16" refractor in 1887. It is listed in RNGC and CGCG (Z204-005) as a galaxy although the RNGC new description reads "R, HISB, STEL, PLN??". In 1985, spectroscopic investigations by Richard Shaw and William Bidelman revealed that N2242 in indeed a previously uncatalogued planetary nebula. So, the RNGC type needs to be changed to 4 (planetary). I observed this object with my 17.5" at 220x and found it faint, small, roundish and estimated its visual magnitude at 14.5. Interestingly, it did not respond to nebular filtration as commonly is the case for planetaries so must have a low excitation.
NGC 2363: Discovered by Copeland and described on 1874, Mar 9 as a "nebulous star or nebulous knot... connected with the principal nebulosity [N2366]." Although it is listed as a galaxy in the UGC (U3847) and MCG (M+12-07-039), the CGCG describes N2363 as a "bright emission patch at the SW end of N2366." The RNGC lists the number as nonexistent with the comment "Patch in N2366, Zwicky" but a more appropriate designation would be 35 – a nebulous region in an external galaxy. With my 13" at 166x, I recorded a mag 14.5 knot in N2366 which on closer inspection was elongated SW-NE. There was a definite contrast gain using an OIII filter.
NGC 2404: This object, discovered by Bigourdan at the Paris Observatory, probably refers to a huge HII region located along the principal eastern arm of the beautiful Sc galaxy N2403 in Camelopardalis. With my 17.5", two spiral arms are clearly visible, attached at opposite ends of the bright central region, both winding almost 180 . The northern arm winds along the eastern side towards the south and ends at a prominent, small, round knot – NGC 2404. Rather than the nonexistent designation the RNGC assigns to N2404, a more appropriate classification would be 35 referring to a nebulous region in an external galaxy.
NGC 3643: This 1865 Marth discovery is located in a small group of galaxies. The RNGC is 0.3 minutes of RA too far E and 3' north of the correct place and should be corrected to 11 20.1 +03 09 (1975). This agrees precisely with the original position given by Marth and given in the RC3.
NGC 4376: This galaxy was discovered by William Herschel (II 530) and the NGC position clearly identifies this galaxy as N4376 = U07498 = M+01-32-053. Both the latter galaxies correctly identify N4376. But based on the position and new description, the RNGC has inadvertently identified N4376 as N4378 which is located 50' south! The corrected 1975 position should read 12 24.0 +05 53 and the new description needs to be changed to refer to this galaxy.
NGC 4641: Discovered by Swift. His discovery position clearly identifies N4641 = U07889 = M+02-32-191, which is located 15' south of N4640 (also discovered by Swift). The declination for N4641 in RNGC is exactly 1 degree too far south. This error is repeated in NGC 2000.0, Deep Sky Field Guide (DSFG) and it is misplotted on Uranometria 2000.0 star atlas. The correct declination is given in UGC, MCG, CGCG and RC3.
NGC 5753, 5754: N5754, discovered by William Herschel as III 687, is the brightest in a close group of four galaxies. This quartet consists of two double systems N5752/5754 and N5753/5755, the first of these pairs being the more southerly. These pairings agree with the descriptions and positions given by Lord Rosse on the 1878, Apr 1 observation of the quartet and were used by Dreyer in the NGC. RNGC has confused the identities of N5753 and N5754, hence the positions and new descriptions for these two entries should be reversed. The correct identifications are given in UGC and MCG.
NGC 6138: Discovered by Stephan in 1870 at Marseilles Observatory. His position is roughly 25' west of N6145 within the rich cluster Abell 2197 and there are only faint stars near this position. The RNGC incorrectly identifies N6138 with the edge-on galaxy M+07-34-020, located 7' north of N6145. Due to large positional discrepancy with Stephan's generally very accurate position, N6138 should be reclassified as nonexistent in the RNGC. None of the other modern catalogues have a listing for N6138.
NGC 6141, 6147: This entry is from Bigourdan and also lies within Abell 2197. The NGC position is 23' SW of N6145. The galaxy identified in the RNGC as N6141 is actually N6147 = M+07-34-023 which is located just east of N6145.
Furthermore, RNGC has probably misidentified N6147 with the extremely faint anonymous galaxy M+07-34-022 (it's more likely M+07-34-023). The Birr Castle observations of the field are not precise enough, though to give a definitive identification of N6147 as both of these faint galaxies are between N6145 and N6146 roughly matching the sketch from 26 May 1849. But in my observation of the field with a 17.5" in dark skies, I was only able to detect M+07-34-023, so this galaxy is a more reasonable match.
Harold Corwin identifies N6141 = Reinmuth 6.106 located at 16 23 06.4 +40 51 30 (2000) which is exactly 3' north of Bigourdan's position. This galaxy is not in MCG, CGCG or RC3 but is listed in DSFG.
NGC 6246, 6246A: Swift's position for N6246 in his list #4 is just 9 sec of RA west of U10580 = M+09-27-098, so this identification is secure. The RNGC has reversed the identifications of N6246 and N6246A = U10584 which is located 10' SSE of N6246. Although these galaxies have similar magnitudes, N6246 is more prominent visually due to a higher surface brightness. The correct identification were noted in RC2 and N6246 is also correctly identified in UGC, MCG and RC3.
NGC 6685: N6685 was discovered by Swift along with NGC 6686 on the same night, the orientation described as SW-NE. Bigourdan later corrected Swift's declination based on his 1888, Aug 2 observation, but kept Swift's original separation and orientation. Howe added a third object, IC 4772, which he placed 2.7' south of N6685. The CGCG (Z228-021), MCG (M+07- 38-015) and UGC (U11317) apparently ignored Bigourdan's correction and have reversed the identifications of N6685 and IC 4772. The RNGC misidentifies N6685 with IC 4772.
NGC 7100, 7101: Bigourdan measured both Marth's N7101 and his nova N7100 on same night. Using his offsets, only single stars are near the position of Bigourdan's N7100. The galaxy identified in the RNGC as N7100 is actually N7101 probably because in the IC 1 notes it was stated that N7101 was "not seen by Spitaler; evidently =7100". Harold Corwin gives a precise position of 21 39 06.9 +08 57 01 (2000) for Bigourdan's star = N7100.
N7101 was discovered by Marth (m448). His declination was 6' too far north but was corrected by Bigourdan. This galaxy (M+01-55-007) is incorrectly identified in CGCG as N7100 instead of N7101. Furthermore, RNGC identifies N7101 with an extremely faint anonymous galaxy close northwest of the actual N7101!
NGC 7353: This object was discovered by Marth as m493. His position is 48 sec of RA following and 2' north of N7348 which was also found by Marth and whose position is correct. There is only a very faint star near Marth's position and Reinmuth could not identify this object. N7353 is incorrectly identified as U12134 in RNGC and RC3 (but not UGC). This galaxy is located 15' SW of N7348, so is not a plausible match.
Harold Corwin suggests a possible candidate at 22 42 12.6 +11 52 39 (2000) although this galaxy is 48 sec of RA east and 3' south (11' ESE) of Marth's place.
NGC 7401, 7402: This pair of galaxies was discovered by Lord Rosse on 1856, Oct 2 in a group containing N7396 (discovered previously by John Herschel) along with the Rosse "novae" N7397 and N7398. This group was examined five times by the Birr Castle observers although this is the only observation in which all five galaxies were recorded with certainty. N7402 was called "doubtful" by Rosse on the 1857, Oct 23 observation although the position given close following N7401 is correct.
The first three NGC entries (N7396, 7397, 7398) have secure identities According to the Rosse sketch, N7401 and N7402 are a close pair, oriented approximately E-W (NGC gives 5 sec of RA separation). This matches up well with N7401 = M+00-58-010 = Z379-013 at 22 52 58.4 +01 08 33 (2000) and N7401 = extremely compact companion 1.5' following at 22 53 04.5 +01 08 39 (2000).
N7401 = M+00-58-010 is identified as N7402 in the MCG, RC3 and DSFG and listed as an anonymous galaxy in the CGCG (Z379-013). RNGC and DSFG reverse the identifications of N7401 and N7402 according to their RA and X coordinates which have N7401 following N7402.
NGC 7738, 7739: This entry is from Secchi who listed 14 objects in his discovery article in AN #1571 although a number of these objects cannot be identified. N7738 and N7739 were given by Secchi with a single position which is reasonable close (30 sec of RA) to U12757. This galaxy is identified as N7738 in RNGC and RC3, N7738 = N7739 in UGC, and as an anonymous galaxy in MCG (M+00-60-038).
The RNGC identifies N7739 as nonexistent but the RA is 0.5 minutes of RA west of N7738 (using Secchi's original position). RC3 tentatively identifies N7739 = Z381-038 at 23 44 30.1 +00 19 12 although this galaxy does make a close pair with N7738 = U12757 (it is 13.7' SSE). Harold Corwin notes that both of these identifications are uncertain.
NGC 7756: In the single Birr Castle observation of N7757 on 1873, Dec 11, Lord Rosse simply described "another neb 5' south preceding". The RNGC incorrectly identifies N7756 with an extremely faint anonymous galaxy located 1' west of N7757 and CGCG incorrectly identifies N7757 as N7756.
Rosse's offset from N7757 corresponds to a star according to RC2 and UGC. More specifically, Harold Corwin suggests N7757 is a 20" pair of mag 14.6/15.1 stars in the GSC with a mean position of 23 48 34.0 +04 05 35. This pair is 5.5' SW of N7757, very close to Rosse's offset. A less likely candidate is a star + faint galaxy at 23 48 28.7 +04 02 58 but this is 8.5' SSW of N7757. In either case, the RNGC identification is clearly in error.
NGC 7840: Discovered by Marth in 1864 as part of a small group of galaxies including NGC's 7830, 7834, 7835, 7837, 7838, 3, 4. With the exception of N7830 which is mostly likely a star, the other members have been identified with faint galaxies. N7840 is listed, though, as nonexistent in RNGC.
Harold Corwin identifies a likely candidate at 00 07 08.9 +08 23 00 (2000). This extremely faint galaxy is less than 3' south of Marth's position. Although I missed viewing this galaxy in my 17.5" and it is not listed in any modern catalogue, it was likely visible to Marth using Lassell's 48" equatorial.