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Over the past couple of years I've been using computerized versions of several catalogues including
Southern Galaxy Catalogue (SGC), Morphological Catalogue of Galaxies (MCG), ESO-Uppsala
Catalogue, Third Reference Catalogue of Bright Galaxies (RC3) and Arizona Database. Using a
database program (Panorama II) on my Macintosh computer has allowed me to quickly compare
identifications among catalogues to find conflicts and also to extract information such as magnitudes,
dimensions, coordinates to organize my personal observing programs. In addition, a computerized
database program is very convenient for keeping observing notes, background information on the objects
obtained from journals or magazines and storing comments about identification problems.
Of particular importance was the publication of the RC3 which contains extensive data on over 23,000 galaxies. In cross-checking the NGC identifications with the various other catalogues listed above (including the RNGC), I ran across a number of inconsistencies in positions and identifications within all the catalogues. In many cases, an initial error (sometimes in the NGC) is simply copied down from one catalogue to the next without anyone rechecking the source material. One of the RC 3 authors, Dr. Harold Corwin investigated several dozen problem cases which I sent him and verified most of these catalogue errors including a number of errors present in the RC3.
In this paper, 27 cases are reviewed involving errors in 30 RNGC listings. This yields a total of 141 cases encompassing 179 errors in this series of articles. Again, I want to thank catalogue sleuths Malcolm Thomson and Harold Corwin for double checking most of these listings, digging up additional information and offering many suggestions.
NGC 324: This galaxy was discovered by John Herschel on 23 October, 1835 at the Cape of Good Hope and described as "F, S, Stellar, the bad definition of a south-easter prevents certainty, but I think it is not a star." His listed coordinates are 00h 54.9m -40 43' (1950). No object exists at this position but exactly 30' south at 00h 54.9m -41 14' is E295-G25, a galaxy that fits Herschel's description and catalogued as N324 in ESO, MCG and RC3.
Instead, RNGC identifies N324 = IC 1609 at 00 57 28 -40 36.1 (1950) which is a possible match but no simple digit error by Herschel would produce these coordinates. As a further complicating factor, the RNGC gives incorrect coordinates for IC 1609 at 00h 56.2m -40 46' (1950). Nothing exists at the RNGC position on the POSS, but the photographic description clearly applies to IC 1609.
Conclusion: Using the ESO/RC3 identification as the most reasonable, the 1975 position should be changed to 00h 56.1m -41 06' and the data updated to describe E295-G25 (1.4'x0.5', PA 95 , 12.9V, 14.0B).
NGC 874: Another discovery by Muller at the Leander-McCormick Observatory and placed at 2h 13.8m -23 25' (1950). He lists this object as mag 15.5 (nucleus), 0.3'x0.1' in PA 170 and as possibly a double star. Additionally, a mag 10 star is 2.8' in PA 320 (NW).
The RNGC lists this object as nonexistent but it is identified in the ESO-Uppsala and RC3 as E478-G18 = M-04-06-019 at 02 13 44.5 -23 32 16 (1950), which is just 7' south of Muller's position. Furthermore, Muller's position angle closely matches the 173 listed in the ESO catalogue and there is a mag 11 star at separation 2.9', although it is NE instead of NW.
Conclusion: This match appears reasonable and data on E478-G18 includes a position of 2h 14.9m -23 25' (1975), dimensions 0.9'x0.5', mag 15.1B.
NGC 901: Marth discovered both N900 and N901 on the same evening in August of 1864 from Malta. His position for N900 is 02 23 33 +26 30 (2000) and is an excellent match for U01843 = M+04-06-020. This galaxy is correctly identified as N900 in the RNGC, UGC, CGCG and RC3 although the MCG incorrectly labels M+04-06-020 = N901.
Marth placed N901 just 3s of RA east and 3' north of N900. The UGC notes for N900 mention a close companion located 2.8' in a position angle of 8 (NNE), though the UGC fails to identify this companion as N901. On the POSS, this faint galaxy appears just below the magnitude cut-off for the CGCG but is a perfect positional match for Marth's N901 and was certainly well within his visual range as it was visible in my 17.5".
The RNGC lists N901 as nonexistent and identical to N900. Interestingly, the coordinates given in the RNGC for N901 are correct as they used the original NGC position from Marth, though for some reason the authors failed to identify this galaxy on the POSS. The GSC position for N901 is 02 23 34.1 +26 33 25 (2000).
NGC 1327: Discovered by Ormond Stone and roughly placed at 3h 25m -25 41' (2000). His description simply includes a magnitude of 16.3 for the nucleus, and the comment "neb?". There is no galaxy at this position and the RNGC lists this number as nonexistent.
The SGC, ESO-LV and RC3 identify N1327 as E481-G26 = M-04-09-008 located at 03 25 23.2 -25 40 46 (2000). The ESO also lists a pair of stars with a wider third star about 8' NW of this galaxy as possibly N1327, although they appear too bright to be Stone's object. This probably is from Stewart's comment in the IC 2 notes "3 vF st close together, no neb".
Considering the generally poor positions at Leander-McCormick Observatory, this galaxy is a good match in position and description. The following data should be used for N1327 = E481-G26 = M-04- 09-008: 3h 24.3 -25 46' (1975), 1.0'x0.3', 15.5B.
NGC 1396: The NGC position from Schmidt is 03h 36.1m -35 50' (1950). There is no galaxy at his position and the RNGC lists N1396 as nonexistent. The SGC and RC3, though, identify a galaxy located in the heart of the Fornax cluster at 03 36 11.2 -35 36 10 (1950). This position is 14' due north of Schmidt's location and places N1396 just 5' west-northwest of the bright elliptical N1399.
Given the size of Schmidt's telescope and other errors in his table, this object is a reasonable match and the only faint galaxy in the immediate vicinity. Additional data includes a 1975 position of 03h 37.1m - 35 31', dimensions 1.0'x0.9' and total blue magnitude of 14.8.
NGC 1412: Found by John Herschel at the Cape of Good Hope on 20 November, 1835 and placed at 03 40 31.2 -26 12 51 (2000). The RNGC lists this object as nonexistent since no galaxy was found at Herschel's position. The ESO-LV and RC3 identify N1412 = E482-G29 at 03 40 29 -26 51.7 (2000), or 40' due south of Herschel's position.
This galaxy is a good match to Herschel's description– "F, S, E, gpmbM, 15", has a * south following distance 2 arcmin" as the galaxy is elongated NW-SE and there is a mag 12 star just under 2' SSE. The poor declination probably resulted from an incorrect digit. Lewis Swift later observed this galaxy and it was recatalogued as IC 1981, this time with the correct position. ESO identifies this galaxy as IC 1981.
So, it is reasonable that N1412 = IC 1981 = E482-G29 and the data in the RNGC should be changed to 3h 39.4m -26 56' (1975), 1.9'x0.8', 13.5B.
NGC 1474: Discovered by Marth in 1864 (m93) and placed at 3h 51.9m +10 25' (1950). This is probably a poor position by Marth as there is no galaxy at these coordinates but 8' north lies U02898 = M+02-10-003 = CGCG 442-005 at 03 51 45.9 +10 33 37 (1950). This galaxy was found by Javelle in 1903 as IC 2002 at Nice Observatory and his micrometric position is accurate. Because of this 8' discrepancy in declination, Javelle must have felt this object was different than m93 = N1474.
The RNGC places N1474 at 3h 51.8 -10 33' (1950), so clearly there is a sign error in declination. The UGC, CGCG, MCG and RC3 identify U02898 = IC 2002 instead of N1474, based on Javelle's accurate placement..
Although Marth's positions are generally more accurate, an 8' error in declination would imply that N1474 = IC 2002. Several other Marth discoveries from the same evening have large errors in RA or declination. So, although the RNGC probably has the correct identification, the declination sign should be reversed and the equivalence made with IC 2002 in the notes column.
NGC 1554, 1555: (Hind's Variable Nebula). The RNGC incorrectly places this faint nebula 1 minute of RA too far east. The position stated in the Sky Catalogue 2000 of 4h 21.8m +19 32' corresponds with the variable T Tauri which illuminates the nebula. So, the RNGC position should be corrected to 4h 20.4m +19 29' (1975).
NGC 2163: This reflection nebula was discovered by Stephan at the Marseilles Observatory. In compiling the NGC, Dreyer accidentally used the declination of N1741 and so the correct identification of N2163 was missed by subsequent catalogues. Dreyer later caught his error and corrected the position in the IC 2 Notes and Corrections section. Brian Skiff has recomputed Stephan's original position using precise coordinates for his offset star HD 41787 as 06 04 53.62 +18 40 08.7 (1950). At this exact location is the reflection nebula Cederblad 62 at 06 04 53.17 +18 39 55.0 just 0.45s in RA and 13".7 in Declination from Stephan's original coordinates!
Besides the excellent positional match, Stephan described N2163 as "elongated with *11 attached south" and visually this nebula appears to extend more prominently north of the mag 11.5 (central) star. On the POSS, Ced 62 is an interesting bipolar nebula with two symmetrical funnel-shaped jets extending north- south from the central star.
In this case it is certain that N2163 = Cederblad 62 at 06 06 21 +18 39 42 (1975) and all data needs to be updated to describe this reflection nebula. Besides listing this object as nonexistent, RNGC reverses the sign of the declination.
NGC 3315: This galaxy was discovered by E.P. Austin of Harvard College (Annals of Harvard Observatory, Vol 13, #207) within the galaxy cluster Hydra I and placed at 10 34 55 -27 30' (1950). No galaxy exists at this position within the cluster and RNGC has identified N3315 = E501-047, located at 10h 34.9m -27 13' (1950).
While this identification is possible, Austin described a "star 1' north-preceding" which does not apply to this galaxy. There is a very bright 5th magnitude star 3' north which would have warranted special mention as it would have interfered with the observation. However, 30' north of Austin's position is E501-G48 = M-04-25-042 at 10 34 58.0 -26 55 52 (1950) which has a 10th magnitude star 1' northwest. Based on Austin's visual description and a probable digit error in declination, this identification appears more likely and is the one used in the ESO-Uppsala and RC3 catalogues.
Assuming N3315 = E501-G48, the 1975 coordinates should be changed to 10h 36.1m -27 04' in the RNGC. Additional data for this galaxy includes dimensions 1.1'x1.0', and magnitude 14.4B.
NGC 3436: Discovered by David Todd (AN 2698, object #6) during his search for a trans-Neptunian planet and very roughly placed at 10h 49m +08 13'(1950). Despite his poor position, several of Todd's "nebulous stars" can be identified based on his field sketches, but I could not find a match for N3436 near Todd's position on the POSS.
The RNGC places N3436 at 10h 39.8 +08 12' (1950) or 8.9 time-minutes west of Todd's position. There is no galaxy listed at this position in any other modern catalogue and I could not identify this object on the POSS. In any case, due to the very large positional discrepancy it appears to be an incorrect identification.
NGC 3565, 3566: Ormond Stone recorded a very faint pair of nebulae at the Leander-McCormick observatory which he gave the same rough position 11h 08m± -19 46' (1950). Dreyer included these two objects as N3565 and N3566. The ESO-Uppsala and RC3 both identify N3565 = N3566 = E570- IG8, an interacting double galaxy located at 11 05 19.7 -19 45 05.3 (1950), essentially two minutes of RA west of Stone's position (typical error in the first discovery list). On the POSS, the images of these two small galaxies are merged and difficult to individually distinguish. So, it is possible that Stone observed this galaxy and a nearby faint star for his second object .
As Sulentic could not find any galaxy at Stone's original position on the POSS, he classified N3565 and N3566 as nonexistent in the RNGC. Assuming N3565 = N3566 = E570-IG8 with a two minute error in RA, the RNGC position for these objects should be changed to 11h 06.6m -19 53' (1975).
NGC 4139, 4140: The NGC entries for N4139 and N4140 are from d'Arrest, who described them as "faint, small, difficult" and the components of a double nebula. Unfortunately, his RA was exactly five minutes of RA too large and both numbers are listed as nonexistent in the RNGC.
When this five minute time correction is applied, the new coordinates coincide precisely with a 1' pair of galaxies, IC 2989 (correctly placed by Bigourdan) and N4077 (from William Herschel), respectively. This pair is in a group of six NGC galaxies along with NGC 4045, 4063, 4073, 4075. In my 17.5", I recorded N4139 = IC 2989 as "faint, very small, elongated 2:1 SW-NE, small bright core, close pair with N4077", while N4140 = N4077 was logged as "fairly faint, oval 4:3 approximately north-south, star at north end." This pair is identified as IC 2989 and N4077 in all modern catalogues.
The RNGC data for N4139 should be changed to 12h 03.3m +01 56' (1975), dimensions 1.0'x0.5' in position angle 30 , mag 14.7B and the notes column should show the equivalence with IC 2989. The "New Description" for N4140 should read "=N4077".
NGC 4604: This object is from by Peters and placed at 12 40 45 -05 08.8 (2000) although the discovery must have been communicated directly to Dreyer as it does not appear in either of his discovery lists in Copernicus.
This object is listed as nonexistent in the RNGC based on Dorothy Carlson's 1939 paper on NGC corrections which states not found at Helwan observatory. The RC3 identifies N4605 = M-01-32-037 at GSC position 12 40 45.2 -05 18 11 (2000) which is exactly 10' south of Peter's position. In my 17.5" I recorded M-01-32-037 as "faint, fairly small, very elongated WSW-ENE, 3rd of 4 in a low power field. Located 11' SSE of N4602." Although, there is no visual description given in the NGC, this identification is reasonable assuming a single digit error in declination by Peters. The RNGC coordinates should be changed to 12h 39.5m -05 10' (1975), dimensions 1.0'x0.4' in PA 75 .
NGC 5070: Discovered by Lewis Swift and placed at 13h 16.3m -12 19' (1950) in a relatively scattered group of six galaxies including NGC 5072, 5076, 5077, 5079, 5088. Nearby N5072, discovered by d'Arrest was accurately placed at 13h 16.6m -12 17' (1950). So, the Swift's position for N5070 is 19s west and 2' south of N5072 (accurately placed by d'Arrest) but there is no object at this position.
The RNGC has identified N5070 with a very faint edge-on galaxy (M-02-34-023) located 3' NNE of N5072. Although imprecise coordinates by Swift could possibly account for this discrepancy, his original discovery description provides another solution: "eeF, eS, vf * v close, looks like a D* at first; another nr; 6 in field." The only galaxy nearby that matches this description is N5072 = M-02-34-022 which has a 14th magnitude star superimposed on the south end causing the initial impression of a faint double star.
So, given Swift's description, N5070 should be listed as nonexistent in the RNGC with new description "=N5072."
NGC 5782: This object was discovered by Lewis Swift on 19 Apr 1887 and placed at 14h 53.2m +11 55' (1950). Bigourdan more accurately measured the position at 14h 53.55m +12 05' (1950) so Swift was off in RA and declination. At Bigourdan's position is U09602 = M+02-38-022 located at 14h 53.5 +12 04'. Further cementing this identification is Swift's description of a "* nr sf" which matches U09602.
The RNGC, CGCG, MCG identify N5782 = M+02-38-021 = Z076-094 located at 14h 52.6m +11 54' (1950) This much fainter galaxy may have been chosen by these catalogues as it differs only in RA from Swift's original position, although this ignores Bigourdan's correction and Swift's description. So, the RNGC coordinates should be changed to 14h 54.7m +11 58' (1975) and the data revised to described U09602 which is a much better match.
NGC 5881: This object was discovered by William Herschel as II 818. In Scientific Papers of William Herschel, Dreyer notes that the listed RA in the GC and NGC was two time-minutes too far east. Because of this error, Bigourdan could not locate N5881. Dreyer's correction places N5881 at 15h 06.2m +63 08' (1950). Less than 1 time-minute further west is IC 1100 (discovered by Swift) at GSC position 15 05 22.4 +63 10 22 (1950) which is the only reasonably bright galaxy in the vicinity.
The RNGC misidentifies N5881 = U09764 but this is clearly erroneous as U09764 is located at 15h 09.8m +65 05' (1950), over 2 from the NGC position. The RNGC coordinates should be changed to 15h 05.9m +63 05' (1975), dimensions 0.8'x0.7', magnitude 14.3B and the notes column should indicate the equivalency with IC 1100.
NGC 6172: Due to an misprint in Stephan's discovery list XIII in AN 2661, the RA is 10 time-minutes too large. The position for his comparison star (SAO 141069) is given correctly as 16 16 19.5 -01 38 55 (2000) and once this correction is applied the recomputed coordinates for N6172 match IC 1213 = U10352 = M+00-42-003 at 16 22 10.3 -01 30 54 (2000). IC 1213 was discovered by Swift and his position is close enough (9s preceding) to pin down his identification.
Because of the error in list XIII the RNGC lists N6172 as nonexistent and U10352 is identified IC 1213 in UGC, MCG and CGCG, although RC 3 lists this galaxy as N6172. The RNGC position should be changed to 16h 20.9m -01 27' (1975). This is an elliptical galaxy with dimensions 1.0'x1.0' and blue magnitude of 13.8.
NGC 6672: Stephan placed N6672 at 18 36 14.6 +42 56 48 (2000) and at this position is a small group of faint stars, the northernmost being an extremely close double. Stephan's description "2 close stars, north one nebulous" verifies the identification as a close double star which Stephan mistook as nebulous. Bigourdan measured an object just 1' from Stephan's position and also described it as "a double star which appears to have a trace of nebulosity."
The RNGC and CGCG misidentify N6672 = Z228-015 at 18h 33.8 +42 48' (2000). This galaxy is almost 40' WSW of Stephan's position! The RNGC type should be changed to nonexistent and the new description changed to "=**".
NGC 6846: The RNGC places this open cluster discovered by Stephan at 19h 56.5m +30 21'(2000). I carefully searched for the cluster at this position but was unsuccessful with my 17.5" telescope in dark skies. When I mentioned my negative result to Connecticut amateur Ernie Ostuno he responded that he located N6846 on the POSS exactly 2 north of the RNGC position at 19h 56.5m +32 21 (2000). Precessing Stephan's original coordinates in AN 1939 shows his position is an exact match for this small clump of stars. The incorrect position in the RNGC is also found in the Lynga #5 catalogue and is repeated in NGC 2000.0, DSFG and on the U2000.0 star atlas.
NGC 7095: Discovered by John Herschel at the Cape of Good Hope on 21 Sept 1837 and placed at 21h 45.3m -81 46' (1950). A few nights later Herschel reobserved the galaxy and confirmed this position. Unfortunately, the General Catalogue and NGC miscopied Herschel's declination, apparently using the north polar distance of N7097 and placed N7095 at 21 35 48 -42 46.3 (1950)
Because of this error the RNGC has misidentified N7095 = E287-G42 located at 21 34 58 -42 49.8 (1950) But precisely at Herschel's original discovery position is the galaxy E27-G1, although the ESO does not assign the NGC designation.
In this case, it is clear that N7095 = E27-G1 at 21 45 48 -81 45.9 (1950) and the RNGC position should be changed to 21h 49.2m -81 39' (1975), dimensions 2.8'x2.7', magnitude 12.2B.
NGC 7255: Another poor position from Leavenworth given as 22h 22m -15 34' (2000) due to the poorly calibrated circles at the Leander-McCormick Observatory. As no object was found near this position the RNGC lists N7255 as nonexistent. Using Leavenworth's discovery sketch, Harold Corwin has positively identified N7255 = M-03-57-006 at 22 23 08.0 -15 32 29 (2000). This implies that Leavenworth's position was roughly 1 minute of RA too far west.
The RNGC position should be changed to 22h 21.7m -15 39' (1975) and data describing M-03-57-006 (dimensions 1.3'x0.4' in position angle 57 ).
NGC 7644: Lewis Swift discovered N7644 and N7651 on separate nights. N7651 appears as #96 in Swift's list 4 at 23h 21.9m +13_ 42' and N7644 is later given as #100 in list 5 in AN 2762 with 1950 coordinates of 23h 20.7m +13_ 42'.
The double system M+02-59-036 = Z431-055 at 23 21 54.6 +13 41 58 (1950) is an excellent match with N7651. The RNGC entries for both N7644 and N7651 refer to the components of this system. But due to relatively large difference in RA, Swift was probably referring to two distinct galaxies. Harold Corwin identifies N7644 as a faint galaxy located west of N7651 at 23 20 57.5 +13 42 11 (1950), which is a good match with Swift's position.
The 1975 position for N7644 should be changed to 23h 22.2m +13 50' and the data changed to describe this galaxy.
NGC 7681: John Herschel's mean position from two observations of h2247 = N7681 is 23 26 23 +17 01 38 (1950). Bigourdan also measured the position of N7681 as 23 26 21 +17 02 52. U12620 = M+03- 59-063 = Z454-074 is located at 23 26 24.0 +17 02 00 (1950), in excellent agreement with Herschel's and Bigourdan's measurements.
Despite this match, the RNGC, RC 3, CGCG, UGC notes and N2000 all misidentify this number as M+03-59-060. This galaxy is located 6.2' WSW of N7681 and is much fainter than U12620. Finally, Herschel mentions "near a double star" which agrees with my visual observation of U12620 as a pair of 11-12 magnitude stars lie 2' northeast. The 1975 RNGC position should to be changed to 23 27 39 +17 10 19 and the data switched to describe U12620.
NGC 7726: Discovered by Lewis Swift on 8 Aug 1886 within the rich galaxy cluster Abell 2634. His discovery position of 23 37 00 +26 42 36 (1950) is 14' ESE of N7720, the brightest member of the cluster.
There is no object near his position and the RNGC has misidentified N7726 with IC 5342 = Z476-092 which was discovered by Howe and correctly placed at 23 36 08 +26 44.1 (1950). This galaxy is one of the several very close companions of N7720 and lies just 2.4' southeast.
As a more plausible candidate for N7726, Harold Corwin has suggested U12721 = MCG +04-55-040= Z476-098 at 23 36 41.4 +26 50 18 (1950) which is closer to Swift's position. This identification is uncertain, though, as Swift mentions a "pB* nr f" and the mag 9 star is actually 9' following although Swift mentioned that N7728 is north-following which does match U12721.
In any case, the RNGC identification is certainly incorrect. Although this identification is not 100% certain, it is a reasonable fit and places N7726 at 23 37.9 +26 59 (1975), dimensions 1.5'x0.5' in PA 60 , mag 15.0B.
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