Celestial Atlas
(NGC 2850 - 2899) ←     NGC Objects: NGC 2900 - 2949 Link for sharing this page on Facebook     → (NGC 2950 - 2999)
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2917, 2918, 2919, 2920, 2921, 2922, 2923, 2924, 2925, 2926, 2927, 2928, 2929, 2930, 2931, 2932, 2933,
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Page last updated Jun 25, 2015
Completed barring future developments, including corresponding PGC page entries

NGC 2900 (= PGC 26974)
Discovered (Mar 10, 1886) by
Lewis Swift
A magnitude 13.0 spiral galaxy (type SBcd?) in Hydra (RA 09 30 15.2, Dec +04 08 39)
Historical Identification: Per Dreyer, NGC 2900 (Swift list III (#45), 1860 RA 09 23 05, NPD 85 15.5) is "most extremely faint, pretty large, round". The position precesses to RA 09 30 24.3, Dec +04 07 48, about 2.5 arcmin east southeast of the galaxy listed above but the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: Based on a recessional velocity of 5340 km/sec, NGC 2900 is about 250 million light years away. Given that and its apparent size of 1.3 by 1.1 arcmin, it is about 95 thousand light years across.
SDSS image of region near spiral galaxy NGC 2900
Above, a 12 arcmin wide SDSS image centered on NGC 2900
Below, a 1.5 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2900

NGC 2901 (= "PGC 5067674")
Recorded (1886) by
Ormond Stone
Looked for but not found (Mar 11, 1891) by Guillaume Bigourdan
Almost certainly a lost or nonexistent object in Leo (RA 09 32 20.6, Dec +31 07 07)
Possibly but not likely to be a double star at RA 09 32 19.1, Dec +31 07 09
Historical Identification: Per Dreyer, NGC 2901 (Ormond Stone list I (#155), 1860 RA 09 24, NPD 58 16±) has "no description". The obviously rough position precesses to RA 09 32 20.6, Dec +31 07 07 (whence the position above), in a completely stellar region. The precessed position is only a third of an arcmin east of a double star of magnitudes 13 and 16 listed as NGC 2901 by Steinicke, but Corwin, noting the rough position and considering that even supposedly accurate positions measured at the Leander McCormick observatory were often well off the mark, feels that what Stone saw was probably one of a number of galaxies within a 2 degree region centered on the NGC position, but that in the absence of any description of the object or its field, what if anything NGC 2901 represents cannot be known. Bigourdan could find nothing in the region, and given his penchant for misidentifying close doubles as nebular objects, his failure to record Steinicke's double star as nebulous appears to confirm Corwin's opinion that it could not be what Stone observed. As a result, although indicating the position of the double for reference purposes, I agree with Corwin's opinion that the object is lost or nonexistent. (Listed in LEDA as an object of unknown nature with designation PGC 5067674, but that designation is not recognized in a search of the LEDA database.)
SDSS image of region near the NGC position of the apparently lost or nonexistent NGC 2901
Above, a 12 arcmin wide SDSS image centered on the NGC position for NGC 2901

NGC 2902 (= PGC 27004 (not =
IC 543))
Discovered (Feb 8, 1785) by Wiliam Herschel
A magnitude 12.2 lenticular galaxy (type SA0(s)?) in Hydra (RA 09 30 52.9, Dec -14 44 09)
Historical Identification: Per Dreyer, NGC 2902 (= GC 1860 = WH III 276, 1860 RA 09 24 12, NPD 104 07.3) is "very faint, very small, stellar". The position precesses to RA 09 30 52.6, Dec -14 44 06, right on the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain. (See IC 543 for a discussion of its misidentification as a duplicate of NGC 2902.)
Physical Information: Based on a recessional velocity of 1995 km/sec, NGC 2902 is about 95 million light years away, in reasonable agreement with widely varying redshift-independent distance estimates of 90 to 190 million light years. Given that and its apparent size of 1.5 by 1.4 arcmin, it is about 40 thousand light years across.
DSS image of region near lenticular galaxy NGC 2902
Above, a 12 arcmin wide DSS image centered on NGC 2902
Below, a 2 arcmin wide DSS image of the galaxy
DSS image of lenticular galaxy NGC 2902

NGC 2903 (= PGC 27077)
Discovered (Nov 16, 1784) by
William Herschel
Also observed (Feb 24, 1827) by John Herschel
A magnitude 9.0 spiral galaxy (type SAB(rs)bc?) in Leo (RA 09 32 10.1, Dec +21 30 03)
Historical Identification: Per Dreyer, NGC 2903 (= GC 1861 = JH 604.1 = WH I 56, 1860 RA 09 24 14, NPD 67 53.1) is "considerably bright, very large, extended, gradually much brighter middle, mottled but not resolved, southwestern of 2", the other being NGC 2905 (which is actually just a star-forming region near the northeastern rim of NGC 2903). The position precesses to RA 09 32 10.3, Dec +21 30 01, right on the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 550 km/sec, NGC 2903 is about 25 million light years away, in good agreement with redshift-independent distance estimates of 20 to 40 million light years. Given that and its apparent size of 11.8 by 4.5 arcmin, it is about 85 thousand light years across. The galaxy contains a number of star-forming regions, one of which has its own NGC listing (NGC 2905, which see).
SDSS image of spiral galaxy NGC 2903
Above, a 12 arcmin wide SDSS image of NGC 2903
Below, a 7 by 11 arcmin wide image emphasizing its dust lanes
(Image Credit Tracey and Russ Birch/Flynn Haase/AURA/NSF/NOAO)

Below, a 15 arcmin wide GALEX X-ray image of the galaxy (Image Credit GALEX/NASA, Wikimedia Commons)
GALEX image of NGC 2903
Below, a detail of the central bar and eastern portion of the galaxy (Image Credit HST, NASA)

Below, a 13 arcmin wide image of the region near the galaxy
(Image Credit & © Jean-Charles Cuillandre (CFHT), Hawaiian Starlight; used by permission)
Canada-France Hawaii Telescope image of region near spiral galaxy NGC 2903

NGC 2904 (= PGC 26981)
Discovered (Mar 30, 1835) by
John Herschel
A magnitude 12.3 spiral galaxy (type E/SAB0?) in Antlia (RA 09 30 17.0, Dec -30 23 06)
Historical Identification: Per Dreyer, NGC 2904 (= GC 1862 = JH 3170, 1860 RA 09 24 15, NPD 119 46.8) is "faint, small, a little extended, pretty suddenly brighter middle". The position precesses to RA 09 30 18.3, Dec -30 23 34, only half an arcmin southeast of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 2340 km/sec, NGC 2904 is about 110 million light years away, in good agreement with redshift-independent distance estimates of 75 to 195 million light years. Given that and its apparent size of 1.5 by 1.0 arcmin, it is about 50 thousand light years across.
DSS image of region near lenticular galaxy NGC 2904
Above, a 12 arcmin wide DSS image centered on NGC 2904
Below, a 2 arcmin wide image of the galaxy (Image Credit Ron Marzke, San Francisco State University)
San Francisco State University image of lenticular galaxy NGC 2904

NGC 2905, a star-forming region in
NGC 2903
Recorded (Nov 16, 1784) by William Herschel
Also observed (Feb 24, 1827) by John Herschel
A star-forming region in Leo (RA 09 32 11.9, Dec +21 31 11)
Historical Identification: Per Dreyer, NGC 2905 (= GC 1863 = JH 604.2 = WH I 57, 1860 RA 09 24 16, NPD 67 52.0) is "very faint, considerably large, round, pretty suddenly bright middle, mottled but not resolved, northeastern of 2", the other being NGC 2903. The position precesses to RA 09 32 12.3, Dec +21 31 07, right on the star-forming region listed above, and its position relative to the nucleus of the galaxy fits the description so the identification is certain.
Physical Information: See NGC 2903 for anything else.
SDSS image of spiral galaxy NGC 2903, showing the location of star-forming region NGC 2905
Above, a 12 arcmin wide SDSS image of NGC 2903, with a box showing the location of NGC 2905
Below, a HST closeup of the eastern portion of the galaxy, with a similar box (Image Credit HST, NASA)
HST image of part of spiral galaxy NGC 2903, showing the location of star-forming region NGC 2905

NGC 2906 (= PGC 27074)
Discovered (Dec 28, 1785) by
William Herschel
Also observed (Dec 25, 1827) by John Herschel
A magnitude 12.7 spiral galaxy (type S(rs)cd? pec) in Leo (RA 09 32 06.2, Dec +08 26 31)
Historical Identification: Per Dreyer, NGC 2906 (= GC 1864 = JH 606 = WH II 495, 1860 RA 09 24 38, NPD 80 57.2) is "faint, pretty small, a little extended, gradually brighter middle". The position precesses to RA 09 32 05.9, Dec +08 25 54, about 0.6 arcmin south of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 2140 km/sec, NGC 2906 is about 100 million light years away, in good agreement with redshift-independent distance estimates of 70 to 140 million light years. Given that and its apparent size of 1.8 by 0.9 arcmin, it is about 50 thousand light years across.
SDSS image of region near spiral galaxy NGC 2906
Above, a 12 arcmin wide SDSS image centered on NGC 2906
Below, a 2.2 SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2906

NGC 2907 (= PGC 27048)
Discovered (Dec 31, 1785) by
William Herschel
Also observed (Dec 16, 1827) by John Herschel
A magnitude 11.6 spiral galaxy (type SA(s)a? pec?) in Hydra (RA 09 31 36.6, Dec -16 44 05)
Historical Identification: Per Dreyer, NGC 2907 (= GC 1865 = JH 607 = WH II 506, 1860 RA 09 25 03, NPD 106 07.5) is "pretty faint, small, a little extended, much brighter to southeast". The position precesses to RA 09 31 39.4, Dec -16 44 24, on the southeastern rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 2090 km/sec, NGC 2907 is about 95 million light years away, in good agreement with a single redshift-independent distance estimate of 90 million light years. Given that and its apparent size of 3.5 by 2.0 arcmin, it is about 95 thousand light years across.
DSS image of region near spiral galaxy NGC 2907
Above, a 12 arcmin wide DSS image centered on NGC 2907
Below, a 4 arcmin wide DSS image of the galaxy
DSS image of spiral galaxy NGC 2907
Below, a 3.8 by 3.2 arcmin wide image of the galaxy
(Image Credit & © Carnegie-Irvine Galaxy Survey; used by permission)
Carnegie-Irvine Galaxy Survey image of spiral galaxy NGC 2907

NGC 2908 (= PGC 27831)
Discovered (Sep 26, 1802) by
William Herschel
Also observed (Mar 23, 1890) by Guillaume Bigourdan
A magnitude 13.3 spiral galaxy (type Sbc?) in Draco (RA 09 43 31.5, Dec +79 42 05)
Historical Identification: Per Dreyer, NGC 2908 (= GC 1866 = WH III 977, 1860 RA 09 25 16, NPD 09 37.5) is "extremely faint, very small". The position precesses to RA 09 43 00.9, Dec +79 44 53, about 2.8 arcmin north northwest of the galaxy listed above, but the description fits and there is nothing comparable nearby so in the absence of any other information the identification would be reasonable, though not at all certain due to the low surface brightness of the galaxy, which has no bright nucleus. However (per Corwin's lengthy discussion of the entry), Herschel made two observations of the object. The first position, (accurately) reduced by Herschel's sister Caroline Herschel, lies (like the NGC position) much closer to a double star of magnitudes 14.5 and 15.1 which is about 3.2 arcmin northwest of the galaxy. Herschel could have easily mistaken the double for a nebulous object, and being a stellar object it would have appeared considerably brighter to him than the galaxy, despite the modern magnitudes being considerably different; so in several ways the double star appears to be a better identification of the NGC object. However, Herschel's second observation, measured from a star closer to his III 977 (and therefore more likely to be accurate) was commented on by Dreyer in his 1912 reanalysis of Herschel's observations, and falls only an arcmin north of the galaxy, making the galaxy seem the better candidate. Dreyer's 1912 comment also states that Bigourdan's position (which precesses to RA 09 43 29.5, Dec +79 42 03, on the western rim of the galaxy listed above) agrees far better with Herschel's second observation, and given the accuracy of his position there is no doubt that Bigourdan observed the galaxy, so there is little doubt that Herschel observed it as well. Given that, the identification of NGC 2908 as PGC 27831 is considered certain, after all.
Additional Notes: The position given above for Bigourdan's observation is not the same as the one Dreyer would have used, as the position Bigourdan listed for his comparison star is over an arcmin south of its correct position (a common problem in those days, as the references available at that time were not as accurate as modern stellar catalogs), and I have used the far more accurate modern position of the star, corrected for proper motion and precessed to his equinox of 1900, to obtain his position for NGC 2908. However, if Bigourdan had been able to use the comparison star's correct position, the agreement between his observation and Herschel's would have been even better, so it does not change Dreyer's comment that Herschel's second observation was in considerably better agreement with Bigourdan's observation, nor alter the argument confirming the identity of NGC 2908 as the galaxy listed above.
Physical Information: Based on a recessional velocity of 6035 km/sec, NGC 2908 is about 280 million light years away. Given that and its apparent size of 0.8 by 0.7 arcmin, it is about 65 thousand light years across.
DSS image of region near spiral galaxy NGC 2908
Above, a 12 arcmin wide DSS image centered on NGC 2908
Below, a 1 arcmin wide DSS image of the galaxy
DSS image of spiral galaxy NGC 2908

NGC 2909 (= "PGC 5067531")
Recorded (Apr 3, 1832) by
John Herschel
Also observed (Jan 28, 1903) by Guillaume Bigourdan
A pair of magnitude 15 stars in Ursa Major (RA 09 37 00.1, Dec +65 56 23)
Historical Identification: Per Dreyer, NGC 2909 (= GC 1867 = JH 605, 1860 RA 09 25 27, NPD 23 26.3) is "extremely faint, small, pretty suddenly brighter middle". The position precesses to RA 09 36 54.4, Dec +65 56 27, in a completely stellar region, so NGC 2909 is almost certainly one of the stellar objects in the region. Per Corwin, the pair listed above (which lies only half an arcmin east of the NGC position) is the most likely candidate, and Bigourdan's position (corrected for a not uncommon error in the position of his comparison star) falls right on that double, which is described by Bigourdan as a double star with an appearance resembling a nebula 20 arcsec in size. As a result, whether that is what Herschel observed or not (per Corwin, many authors have suggested different candidates), the double is not only the most obvious candidate but also has more than a century of tradition making it as good a candidate for NGC 2909 as anything else.
Physical Information: The stars are listed as magnitude 15.0 and 15.2, with a separation of 14 arcsec. Listed in LEDA as a pair of stars with designation PGC 5067531, but that designation is not recognized by a search of the LEDA database.
SDSS image of region near the pair of stars listed as NGC 2909
Above, a 12 arcmin wide SDSS image centered on the pair of stars listed as NGC 2909

NGC 2910 (= OCL 781 = "PGC 3518273")
Discovered (Apr 10, 1834) by
John Herschel
A magnitude 7.2 open cluster (type I2p) in Vela (RA 09 30 30, Dec -52 55 30)
Historical Identification: Per Dreyer, NGC 2910 (= GC 1868 = JH 3171, 1860 RA 09 25 37, NPD 142 17.4) is a "cluster, considerably large, pretty rich, pretty compressed, stars from 10th to 14th magnitude". The position precesses to RA 09 30 16.6, Dec -52 54 15, within the northwestern rim of the cluster listed above and the description fits, so the identification is certain.
Discovery Notes: Corwin notes that Herschel made three observations of the cluster, and obtained three different positions; but all are within the boundaries of the cluster, and as already noted what we see fits his description, so despite his difficulty in deciding where to place the center of the cluster, there is no doubt that what Herschel saw on all three occasions was the same cluster described here.
Physical Information: NGC 2910 is about 8500 light years away. It contains 30 or so moderately bright stars irregularly scattered across a region 5 or 6 arcmin across, concentrated on the eastern rim of the roughly circular region. Given its distance and apparent size, it spans 12 to 15 light years. Listed in LEDA as an object of unknown nature with designation PGC 3518273, but that designation is not recognized by a search of the LEDA database.
DSS image of region near open cluster NGC 2910
Above, a 12 arcmin wide DSS image centered on NGC 2910

NGC 2911 (= PGC 27159 =
Arp 232)
Discovered (Mar 11, 1784) by William Herschel
Also observed (January 1828) by John Herschel
A magnitude 11.5 lenticular galaxy (type SA0(rs)a? pec) in Leo (RA 09 33 46.1, Dec +10 09 09)
Historical Identification: Per Dreyer, NGC 2911 (= GC 1869 = JH 608 = WH II 40, 1860 RA 09 26 15, NPD 79 13.8) is "faint, pretty large, round, gradually brighter middle, western of 2", the other being NGC 2914. The position precesses to RA 09 33 46.3, Dec +10 09 06, nearly dead center on the galaxy listed above, the description fits and there is nothing else nearby save for NGC 2914, so the identification is certain.
Physical Information: Based on a recessional velocity of 3185 km/sec, NGC 2911 is about 150 million light years away, in reasonable agreement with wildly varying redshift-independendent distance estimates of 155 to 1280 million light years. Given that and its apparent size of 3.8 by 2.1 arcmin (including its fainter, distorted outer regions), it is about 165 thousand light years across. NGC 2911 is listed as a Seyfert galaxy, and is used by the Arp Atlas as an example of a galaxy with concentric rings.
SDSS image of region near lenticular galaxy NGC 2911, also known as Arp 232; also shown are NGC 2914 and the star listed as NGC 2912
Above, a 12 arcmin wide SDSS image centered on NGC 2911, also showing NGC 2912 and 2914
Below, a 3.8 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2911, also known as Arp 232

NGC 2912 (= PGC 3325919)
Discovered (Apr 3, 1870) by
Herman Schultz
A magnitude 14.4 star in Leo (RA 09 33 56.9, Dec +10 11 32)
Historical Identification: Per Dreyer, NGC 2912 (= GC 5488, Schultz, 1860 RA 09 26 18, NPD 79 12) is "extremely faint, h608 to the southwest", h608 being NGC 2911. The position precesses to RA 09 33 49.4, Dec +10 10 53, but there is nothing there. The key to identifying the object is Schultz' additional note "some seconds to the east and 2 arcmin north of h608". That places the object a bit further north than the NGC position, and (per Corwin) the only object in the region to the northeast of NGC 2911 that Schultz could have seen is the star listed above, so the identification is reasonably certain. In any event it cannot be PGC 27167, which is sometimes misidentified as NGC 2912, because that galaxy is too faint for Schultz to have seen and is not north of NGC 2911, but nearly due east of it; still, since it is sometimes misidentified as NGC 2912, it is discussed in the following entry. (NGC 2912 is listed in LEDA as a star with designation PGC 3325919.)
SDSS image of region near the star listed as NGC 2912, also showing NGC 2911 and NGC 2912 and PGC 27167, which is sometimes misidentified as NGC 2912
Above, a 12 arcmin wide SDSS image centered on NGC 2912, also showing NGC 2911 & 2914 & PGC 27167

PGC 27167 (not =
NGC 2912)
Not an NGC object but listed here since sometimes misidentified as NGC 2912
A magnitude 17(?) irregular galaxy (type Im?) in Leo (RA 09 33 51.3, Dec +10 09 34)
Historical Misidentification: As noted in the entry for NGC 2912, PGC 27167 is sometimes misidentified as that object; but it is too faint for Schultz to have seen, and instead of being well to the northeast of NGC 2911 it is nearly due east, so it cannot be the NGC object.
Physical Information: Based on a recessional velocity of 3440 km/sec, PGC 27167 is about 160 million light years away. Given that and its apparent size of 0.3 by 0.3 arcmin, it is about 14 thousand light years across.
SDSS image of irregular galaxy PGC 27167, which is sometimes misidentified as NGC 2912
Above, a 0.6 arcmin wide SDSS image of PGC 27167; for a wide-field view see NGC 2912

NGC 2913 (= PGC 27184)
Discovered (Mar 10, 1864) by
Albert Marth
A magnitude 13.4 spiral galaxy (type Sc?) in Leo (RA 09 34 02.7, Dec +09 28 45)
Historical Identification: Per Dreyer, NGC 2913 (= GC 5489, Marth 169, 1860 RA 09 26 29, NPD 79 54) is "very faint, pretty large, irregularly round". The position precesses to RA 09 33 58.9, Dec +09 28 52, less than an arcmin west of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 3055 km/sec, NGC 2913 is about 140 million light years away, in reasonable agreement with redshift-independent distance estimates of 150 to 185 million light years. Given that and its apparent size of 1.05 by 0.65 arcmin, it is about 45 thousand light years across.
SDSS image of region near spiral galaxy NGC 2913
Above, a 12 arcmin wide SDSS image centered on NGC 2913
Below, a 1.2 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2913

NGC 2914 (= PGC 27185 =
Arp 137)
Discovered (Mar 3, 1786) by William Herschel
Also observed (January 1828) by John Herschel
A magnitude 13.2 lenticular galaxy (type SB0(rs)a? pec) in Leo (RA 09 34 02.8, Dec +10 06 32)
Historical Identification: Per Dreyer, NGC 2914 (= GC 1870 = JH 609 = WH III 513, 1860 RA 09 26 32, NPD 79 16.4) is "very faint, small, round, brighter middle and nucleus, eastern of 2", the other being NGC 2911. The position precesses to RA 09 34 03.2, Dec +10 06 27, on the eastern rim of the galaxy listed above, the description fits and there is nothing else nearby save for the aforementioned NGC 2911, so the identification is certain.
Physical Information: Based on a recessional velocity of 3160 km/sec, NGC 2914 is about 145 million light years away, in good agreement with redshift-independent distance estimates of 110 to 150 million light years. Given that and its apparent size of 1.0 by 0.55, the galaxy is about 40 thousand light years across. NGC 2914 is used by the Arp Atlas as an example of material emanating from elliptical galaxies. Based on the closeup below, it may be a polar ring galaxy.
SDSS image of region near lenticular galaxy NGC 2914, also known as Arp 137; also shown are NGC 2911 and the star listed as NGC 2912
Above, a 12 arcmin wide SDSS image centered on NGC 2914, also showing NGC 2911 and 2912
Below, a 1.4 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2914, also known as Arp 137

NGC 2915 (= PGC 26761)
Discovered (Mar 31, 1837) by
John Herschel
A magnitude 12.7 spiral galaxy (type SBab? pec) in Chamaeleon (RA 09 26 11.8, Dec -76 37 38)
Historical Identification: Per Dreyer, NGC 2915 (= GC 1871 = JH 3174, 1860 RA 09 26 54, NPD 166 00.8) is "pretty faint, pretty large, round, gradually brighter middle". The position precesses to RA 09 26 07.0, Dec -76 37 29, on the western rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 470 km/sec, NGC 2915 is about 20 million light years away, in reasonable agreement with redshift-independent distance estimates of 10 to 17 million light years. Using the most commonly accepted distance of 15 million light years and its apparent size of 1.1 by 0.7 arcmin, its core is about 5 thousand light years across. NGC 2915 is the darkest spiral galaxy known, only its apparently irregular core being observable in visible light; but radio emissions from neutral hydrogen atoms show that it is actually a complex spiral with a gas-filled disk extending far beyond the visible core (that disk spans an area about 22 by 17 arcmin in size, corresponding to 95 thousand light years).
DSS image of region near peculiar spiral galaxy NGC 2915
Above, a 12 arcmin wide DSS image centered on NGC 2915
Below, a 1.5 arcmin wide DSS image of the core of the galaxy
DSS image of core of peculiar spiral galaxy NGC 2915
Below, a 1.5 arcmin wide HST image of the core of the galaxy (Image Credit Hubble Legacy Archive)
'Raw' HST image of the core of peculiar spiral galaxy NGC 2915
Below, a 20 by 17 arcmin wide composite of visible-light (yellow) and radio (blue) images of NGC 2915 (Image Credit G. R. Meurer (Johns Hopkins U.), C. Carignan (U. Montreal), S. Beaulieu and K. Freeman (MSSSO), Radio Image: ATCA, Optical Image: AAT) (Image superimposed on a DSS background to establish the scale, and partially fill in the background)
Composite of radio and visible-light images of spiral galaxy NGC 2915, showing the immense spiral disk visible only in radio emission from neutral hydrogen atoms superimposed on a visible light image of the region

NGC 2916 (= PGC 27244)
Discovered (Nov 16, 1784) by
William Herschel
Also observed (Feb 24, 1827) by John Herschel
A magnitude 12.1 spiral galaxy (type SA(rs)b?) in Leo (RA 09 34 57.6, Dec +21 42 19)
Historical Identification: Per Dreyer, NGC 2916 (= GC 1872 = JH 610 = WH II 260, 1860 RA 09 26 59, NPD 67 40.5) is "faint, small, very little extended". The position precesses to RA 09 34 55.1, Dec +21 42 17, on the western rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 3730 km/sec, NGC 2916 is about 175 million light years away, in good agreement with redshift-independent distance estimates of 130 to 185 million light years. Given that and its apparent size of 2.7 by 1.4 arcmin, it is about 135 thousand light years across.
SDSS image of region near spiral galaxy NGC 2916
Above, a 12 arcmin wide SDSS image centered on NGC 2916
Below, a 2.7 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2916

NGC 2917 (= PGC 27207)
Discovered (Feb 6, 1864) by
Albert Marth (170)
A magnitude 13.6 lenticular galaxy (type SAB0(rs)a?) in Hydra (RA 09 34 26.9, Dec -02 30 15)
Historical Identification: Per Dreyer, NGC 2917 (= GC 5491, Marth 170, 1860 RA 09 27 21, NPD 91 53) is "pretty faint, small, much brighter middle". The position precesses to RA 09 34 26.9, Dec -02 30 13, right on the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 3675 km/sec, NGC 2917 is about 170 million light years away. Given that and its apparent size of 1.3 by 0.35 arcmin, it is about 65 thousand light years across. (The NED also lists a second recessional velocity of about 5390 km/sec, which would correspond to a distance of about 250 million light years and make it about 95 thousand light years across. Unfortunately, in the absence of any other distance estimate, which if either of the two distances is correct is merely a matter of speculation.)
SDSS image of region near lenticular galaxy NGC 2917
Above, a 12 arcmin wide SDSS image centered on NGC 2917
Below, a 1.6 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2917

NGC 2918 (= PGC 27282)
Discovered (Mar 13, 1785) by
William Herschel
Also observed (Jan 27, 1827) by John Herschel
A magnitude 12.6 lenticular galaxy (type E/S0?) in Leo (RA 09 35 44.1, Dec +31 42 20)
Historical Identification: Per Dreyer, NGC 2918 (= GC 1873 = JH 611 = WH III 298, 1860 RA 09 27 24, NPD 57 41.0) is "very faint, considerably small, round, suddenly brighter middle and nucleus". The position precesses to RA 09 35 44.8, Dec +31 41 42, only 0.6 arcmin south of the center of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 6840 km/sec, NGC 2918 is about 320 million light years away. Given that and its apparent size of 1.3 by 0.8 arcmin, it is about 120 thousand light years across.
SDSS image of region near lenticular galaxy NGC 2918
Above, a 12 arcmin wide SDSS image centered on NGC 2918
Below, a 1.6 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2918

NGC 2919 (= PGC 27232)
Discovered (Feb 1, 1877) by
Wilhelm Tempel
A magnitude 12.9 spiral galaxy (type SAB(rs)bc?) in Leo (RA 09 34 47.5, Dec +10 17 01)
Historical Identification: Per Dreyer, NGC 2919 (= GC 5490, Tempel list I (#24 = list V#4), 1860 RA 09 27 38, NPD 79 05.9) is "faint, pretty small". The position precesses to RA 09 35 09.4, Dec +10 16 49, over 5 arcmin east of the galaxy listed above. However, the position given in Tempel's list I (and used in Dreyer's NGC entry) was merely an estimate, and the micrometrically measured position in his list V [= (1882) RA 09 28 26.9, Dec +10 48 26] precesses to RA 09 34 47.3, Dec +10 16 59, practically dead center on the galaxy, and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 2430 km/sec, NGC 2919 is about 115 million light years away, in reasonable agreement with redshift-independent distance estimates of 115 to 165 million light years. Given that and its apparent size of 1.6 by 0.6 arcmin, it is about 55 thousand light years across.
SDSS image of region near spiral galaxy NGC 2919
Above, a 12 arcmin wide SDSS image centered on NGC 2919
Below, a 1.8 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2919

NGC 2920 (= PGC 27197)
Discovered (Feb 1, 1837) by
John Herschel
A magnitude 13.1 spiral galaxy (type Sa? pec?) in Hydra (RA 09 34 12.2, Dec -20 51 33)
Historical Identification: Per Dreyer, NGC 2920 (= GC 1874 = JH 3172, 1860 RA 09 27 49, NPD 110 13.9) is "extremely faint, small, round, western of 2", the other being NGC 2921. The position precesses to RA 09 34 16.8, Dec -20 51 08, a little over an arcmin east northeast of the galaxy listed above, the description fits and there is nothing else nearby save the aforementioned NGC 2921, so the identification is certain.
Physical Information: Based on a recessional velocity of 3305 km/sec, NGC 2920 is about 155 million light years away. Given that and its apparent size of 0.9 by 0.6 arcmin, it is about 45 thousand light years across.
DSS image of region near spiral galaxy NGC 2920, also showing NGC 2921
Above, a 12 arcmin wide DSS image centered on NGC 2920, also showing NGC 2921
Below, a 1 arcmin wide DSS image of the galaxy
DSS image of spiral galaxy NGC 2920

NGC 2921 (= PGC 27214)
Discovered (Dec 24, 1786) by
William Herschel
Also observed (Mar 23, 1835) by John Herschel
A magnitude 12.0 spiral galaxy (type (R)SAB(rs)a? pec) in Hydra (RA 09 34 31.6, Dec -20 55 13)
Historical Identification: Per Dreyer, NGC 2921 (= GC 1875 = JH 3173 = WH III 597, 1860 RA 09 28 02, NPD 110 18.0) is "very faint, pretty small, a little extended, very gradually a little brighter middle, eastern of 2", the other being NGC 2920. The position precesses to RA 09 34 29.7, Dec -20 55 16, on the western rim of the nucleus of the galaxy listed above, the description fits and the only thing else nearby is the aforementioned NGC 2920, so the identification is certain.
Physical Information: Based on a recessional velocity of 2960 km/sec, NGC 2921 is about 140 million light years away, in reasonable agreement with redshift-independent distance estimates of about 145 to 160 million light years. Given that and its apparent size of 3.3 by 1.0 arcmin, it is about 130 thousand light years across.
DSS image of region near spiral galaxy NGC 2921, also showing NGC 2920
Above, a 12 arcmin wide DSS image centered on NGC 2921, also showing NGC 2920
Below, a 3.6 arcmin wide DSS image of the galaxy
DSS image of spiral galaxy NGC 2921

NGC 2922 (= PGC 27361)
Discovered (Mar 18, 1884) by
Édouard Stephan
A magnitude 14.0 spiral galaxy (type SB(s)bc? pec) in Leo Minor (RA 09 36 52.4, Dec +37 41 42)
Historical Identification: Per Dreyer, NGC 2922 (Stephan list XIII (#48), 1860 RA 09 28 15, NPD 51 40.8) is "very faint, small, irregularly round, a little brighter middle, mottled but not resolved". The position precesses to RA 09 36 53.0, Dec +37 41 47, on the northern rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 4370 km/sec, NGC 2922 is about 205 million light years away. Given that and its apparent size of 1.2 by 0.45 arcmin, it is about 70 thousand light years across.
SDSS image of region near spiral galaxy NGC 2922
Above, a 12 arcmin wide SDSS image centered on NGC 2922
Below, a 1.4 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2922

NGC 2923 (= PGC 27306)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 14.2 spiral galaxy (type SAB(rs)b?) in Leo (RA 09 36 03.8, Dec +16 45 37)
Historical Identification: Per Dreyer, NGC 2923 (= GC 5492, Marth 171, 1860 RA 09 28 17, NPD 72 35) is "very faint". The position precesses to RA 09 36 01.9, Dec +16 47 38, about 2 arcmin north northwest of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 8205 km/sec, a straightforward calculation indicates that NGC 2923 is about 380 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 370 million light years away at the time the light by which we see it was emitted, about 375 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.6 by 0.45 arcmin, the galaxy is about 65 thousand light years across.
SDSS image of region near spiral galaxy NGC 2923
Above, a 12 arcmin wide SDSS image centered on NGC 2923
Below, a 0.8 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2923

NGC 2924 (= PGC 27253)
Discovered (Feb 12, 1836) by
John Herschel
A magnitude 12.0 elliptical galaxy (type E0?) in Hydra (RA 09 35 10.8, Dec -16 23 54)
Historical Identification: Per Dreyer, NGC 2924 (= GC 1876 = JH 3175, 1860 RA 09 28 32, NPD 105 46.7) is "pretty bright, small, round". The position precesses to RA 09 35 09.8, Dec -16 24 02, on the southwestern rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 4335 km/sec, NGC 2921 is about 200 million light years away, well beyond redshift-independent distance estimates of about 50 to 105 million light years. Based on the Hubble distance and its apparent size of 1.7 by 1.7 arcmin, it is about 100 thousand light years across, but if the redshift-independent distance estimates are more accurate it is only about half that size.
DSS image of region near elliptical galaxy NGC 2924, also showing IC 546
Above, a 12 arcmin wide DSS image centered on NGC 2924, also showing IC 546
Below, a 2.4 arcmin wide DSS image of the galaxy
DSS image of elliptical galaxy NGC 2924

NGC 2925 (= OCL 783 = "PGC 3518274")
Discovered (Jan 5, 1837) by
John Herschel
A magnitude 8.3 open cluster (type III1p) in Vela (RA 09 33 09, Dec -53 23 42)
Historical Identification: Per Dreyer, NGC 2925 (= GC 1877 = JH 3177, 1860 RA 09 28 57, NPD 142 49.4) is a "cluster, pretty rich, pretty compressed, double star taken", the last comment meaning that the position of the double star on the cluster's southeastern margin was used as the position of the cluster. The position precesses to RA 09 33 36.5, Dec -53 26 40, almost 3 arcmin east northeast of the double star in question, but still near the southeastern outline of the cluster and there is nothing comparable nearby, so the identification is certain.
Physical Information: NGC 2925 is about 2500 light years away. Its 40 or so brighter stars span a region about 14 by 12 arcmin wide, which corresponds to about 10 light years. It is listed in LEDA as an unknown type of object with designation PGC 3518274, but that designation is not recognized by a search of the LEDA database.
DSS image of region near open cluster NGC 2925
Above, a 20 arcmin wide DSS image centered on NGC 2925

NGC 2926 (= PGC 27400)
Discovered (Mar 27, 1886) by
Johann Palisa
A magnitude 13.6 spiral galaxy (type SAB(rs)bc?) in Leo (RA 09 37 31.0, Dec +32 50 29)
Historical Identification: Per Dreyer, NGC 2926 (Palisa (#2), 1860 RA 09 29 08, NPD 56 32.0) is "very faint". The position precesses to RA 09 37 31.3, Dec +32 50 29, right on the galaxy listed above and there is nothing else nearby, so the identification is certain.
Physical Information: Based on a recessional velocity of 4360 km/sec, NGC 2926 is about 205 million light years away. Given that and its apparent size of 1.0 by 0.7 arcmin, it is about 60 thousand light years across.
SDSS image of region near spiral galaxy NGC 2926
Above, a 12 arcmin wide SDSS image centered on NGC 2926
Below, a 1.2 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2926

NGC 2927 (= PGC 27385)
Discovered (Feb 21, 1863) by
Heinrich d'Arrest
A magnitiude 12.9 spiral galaxy (type SAB(rs)b?) in Leo (RA 09 37 15.2, Dec +23 35 26)
Historical Identification: Per Dreyer, NGC 2927 (= GC 5493, d'Arrest, 1860 RA 09 29 18, NPD 65 47.1) is "faint, pretty large, round, a little brighter middle". The position precesses to RA 09 37 17.8, Dec +23 35 23, just off the eastern rim of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 7545 km/sec, a straightforward calculation indicates that NGC 2927 is about 350 million light years away, in reasonable agreement with redshift-independent distance estimates of 370 to 400 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 340 million light years away at the time the light by which we see it was emitted, about 345 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 1.7 by 1.0 arcmin, the galaxy is about 170 thousand light years across.
SDSS image of region near spiral galaxy NGC 2927
Above, a 12 arcmin wide SDSS image centered on NGC 2927
Below, a 1.8 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2927

NGC 2928 (= PGC 27380)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 14.7 spiral galaxy (type SB(rs)bc?) in Leo (RA 09 37 10.1, Dec +16 58 38)
Historical Identification: Per Dreyer, NGC 2928 (= GC 5494, Marth 172, 1860 RA 09 29 22, NPD 72 23) is "very faint, small, round, brighter middle". The position precesses to RA 09 37 07.1, Dec +16 59 30, just over an arcmin northwest of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 8330 km/sec, a straightforward calculation indicates that NGC 2928 is about 390 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 375 million light years away at the time the light by which we see it was emitted, about 380 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 1.25 by 1.1 arcmin, the galaxy is about 135 thousand light years across.
SDSS image of region near spiral galaxy NGC 2928
Above, a 12 arcmin wide SDSS image centered on NGC 2928
Below, a 1.6 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2928

NGC 2929 (= PGC 27398)
Discovered (Feb 21, 1863) by
Heinrich d'Arrest
A magnitude 13.8 spiral galaxy (type Sbc?) in Leo (RA 09 37 29.9, Dec +23 09 42)
Historical Identification: Per Dreyer, NGC 2929 (= GC 1878, d'Arrest, 1860 RA 09 29 32, NPD 66 12.5) is "extremely faint, very small, a little extended, very little brighter middle, 1st of 3", the others being NGC 2930 and 2931. The position precesses to RA 09 37 30.7, Dec +23 09 58, only 0.3 northeast of the center of the galaxy listed above and barely outside its outline, the description fits (including the two galaxies to its north northeast) and there is nothing nearby save for the aforementioned NGC objects, so the identification is certain.
Physical Information: Based on a recessional velocity of 7510 km/sec, a straightforward calculation indicates that NGC 2929 is about 350 million light years away, in good agreement with redshift-independent distance estimates of 325 to 370 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 340 million light years away at the time the light by which we see it was emitted, about 345 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 1.25 by 0.35 arcmin, it is about 125 thousand light years across.
SDSS image of region near spiral galaxy NGC 2929, also showing NGC 2930 and NGC 2931
Above, a 12 arcmin wide SDSS image centered on NGC 2929, also showing NGC 2930 and 2931
Below, a 1.4 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2929

NGC 2930 (= PGC 27404)
Discovered (Feb 21, 1863) by
Heinrich d'Arrest
A magnitude 14.2 spiral galaxy (type Scd? pec) in Leo (RA 09 37 32.8, Dec +23 12 12)
Historical Identification: Per Dreyer, NGC 2930 (= GC 1879, d'Arrest, 1860 RA 09 29 33, NPD 66 10.2) is "extremely faint, small, 2nd of 3", the others being NGC 2929 and 2931. The position precesses to RA 09 37 31.8, Dec +23 12 16, on the western rim of the galaxy listed above, the description fits and there is nothing nearby save for the aforementioned NGC objects so the identification is certain.
Physical Information: Based on a recessional velocity of 7380 km/sec, a straightforward calculation indicates that NGC 2929 is about 345 million light years away, in reasonable agreement with widely varying redshift-independent distance estimates of 105 to 345 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 335 million light years away at the time the light by which we see it was emitted, about 340 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.8 by 0.45 arcmin, it is about 80 thousand light years across. (The NED lists a second recessional velocity of 6600 km/sec, which would correspond to a distance of only 305 million light years and a size of 70 thousand light years, but given the wide range of other distance estimates there is no way to know which if either of the recessional velocities is the correct one.) The peculiar appearance of the central part of the galaxy suggests that it is probably a starburst galaxy, and it has been suggested that both its distorted appearance and active star-forming regions are the result of a merger of two smaller galaxies.
SDSS image of region near spiral galaxy NGC 2930, also showing NGC 2929 and NGC 2931
Above, a 12 arcmin wide SDSS image centered on NGC 2930, also showing NGC 2929 and 2931
Below, a 0.9 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2930

NGC 2931 (= PGC 27415)
Discovered (Feb 21, 1863) by
Heinrich d'Arrest
A magnitude 14.2 spiral galaxy (type Sbc?) in Leo (RA 09 37 37.7, Dec +23 14 27)
Historical Identification: Per Dreyer, NGC 2931 (= GC 1880, d'Arrest, 1860 RA 09 29 41, NPD 66 07.8) is "extremely faint, very small, 3rd of 3", the others being NGC 2929 and 2930. The position precesses to RA 09 37 39.9, Dec +23 14 39, only half an arcmin north of the galaxy listed above, the description fits and there is nothing nearby save for the aforementioned NGC objects so the identification is certain.
Physical Information: Based on a recessional velocity of 7495 km/sec, a straightforward calculation indicates that NGC 2931 is about 350 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 340 million light years away at the time the light by which we see it was emitted, about 345 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.7 by 0.5 arcmin, it is about 70 thousand light years across.
SDSS image of region near spiral galaxy NGC 2931, also showing NGC 2929 and NGC 2930
Above, a 12 arcmin wide SDSS image centered on NGC 2931, also showing NGC 2929 and 2930
Below, a 0.9 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2931

NGC 2932 (= "PGC 5067532")
Discovered (Mar 3, 1837) by
John Herschel
A group of stars in Vela (RA 09 35 54, Dec -46 55 00)
Historical Identification: Per Dreyer, NGC 2932 (= GC 1881 = JH 3179, 1860 RA 09 30 07, NPD 136 19.0) is a "cluster, extremely large, very rich, stars large and small (meaning bright and faint)". The position precesses to RA 09 35 18.6, Dec -46 56 27, well within the outline of the very large scattering of stars listed above, which is generally recognized as NGC 2932 despite the difficulty of seeing it at all against the crowded stellar background shown on modern photographs of the region.
Physical Information: Per Corwin, Herschel described the grouping as "... a degree or degree and half in diameter, very rich in stars of all magnitudes from 8 m downwards...". It is probably just a random scattering of stars rather than a physical cluster, hence its designation as a group perhaps a degree or so across. (It is listed in LEDA as an unknown type of object with designation PGC 5067532, but that designation is not recognized by a search of the LEDA database.)
DSS image of region near the scattered group of stars listed as NGC 2932
Above, a 1 degree wide DSS image centered on the group of stars listed as NGC 2932

NGC 2933 (= PGC 27436)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 14.6 spiral galaxy (type SB(rs)bc? pec) in Leo (RA 09 37 55.0, Dec +17 00 53)
Historical Identification: Per Dreyer, NGC 2933 (= GC 5495, Marth 173, 1860 RA 09 30 10, NPD 72 20) is "faint, very small, a little extended, southwestern of 2", the other being NGC 2934. The position precesses to RA 09 37 55.0, Dec +17 02 24, about 1.5 arcmin north of the galaxy listed above, but the description fits, there is nothing comparable nearby and the fact that Marth's position for NGC 2934 had a similar error makes the identification of both objects certain. (Odds are that despite the passage of a year between the two observations he used the same comparison star (perhaps one of the two to the south of the galaxies), and it had an error in its recorded position.)
Physical Information: Based on a recessional velocity of 4335 km/sec, NGC 2933 is about 200 million light years away. Given that and its apparent size of 0.95 by 0.35 arcmin, it is about 55 thousand light years across.
SDSS image of region near spiral galaxy NGC 2933, also showing NGC 2934
Above, a 12 arcmin wide SDSS image centered on NGC 2933, also showing NGC 2934
Below, a 1 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2933

NGC 2934 (= PGC 1523531)
Discovered (Apr 2, 1865) by
Albert Marth
A magnitude 16.0 lenticular galaxy (type SB0? pec) in Leo (RA 09 37 55.2, Dec +17 03 16)
Historical Identification: Per Dreyer, NGC 2934 (= GC 5496, Marth 174, 1860 RA 09 30 13, NPD 72 18) is "extremely faint, northeastern of 2", the other being NGC 2933. The position precesses to RA 09 37 58.1, Dec +17 04 24, about 1.4 arcmin north northeast of the galaxy listed above, and although there are similar candidates to the northwest of Marth's position, the fact that his position for NGC 2933 had a similar error makes the identification of both objects certain. (Odds are that despite the passage of a year between the two observations he used the same comparison star (perhaps one of the two to the south of the galaxies), and it had an error in its recorded position.)
Physical Information: Based on a recessional velocity of 8100 km/sec, a straightforward calculation indicates that NGC 2934 is about 375 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 365 million light years away at the time the light by which we see it was emitted, about 370 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.5 by 0.25 arcmin, it is about 55 thousand light years across.
SDSS image of region near lenticular galaxy NGC 2934, also showing NGC 2933
Above, a 12 arcmin wide SDSS image centered on NGC 2934, also showing NGC 2933
Below, a 0.6 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2934

NGC 2935 (= PGC 27351)
Discovered (Mar 20, 1786) by
William Herschel
Also observed (Mar 23, 1835) by John Herschel
A magnitude 11.3 spiral galaxy (type (R)SAB(s)b?) in Hydra (RA 09 36 44.9, Dec -21 07 42)
Historical Identification: Per Dreyer, NGC 2935 (= GC 1882 = JH 3178 = WH II 556. 1860 RA 09 30 17, NPD 110 30.1) is "pretty bright, pretty small, very little extended, gradually much brighter middle". The position precesses to RA 09 36 44.8, Dec -21 07 38, right on the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 2270 km/sec, NGC 2935 is about 105 million light years away, in good agreement with redshift-independent distance estimates of 80 to 120 million light years. Given that and its apparent size of 4.5 by 4.0 arcmin, it is about 135 thousand light years across.
NOAO image of region near spiral galaxy NGC 2935 superimposed on a DSS background to fill in missing areas
Above, a 12 arcmin wide image centered on NGC 2935
(Image Credit Adam Block/NOAO/AURA/NSF; superimposed on a DSS background to fill in missing areas)
Below, a 5 arcmin wide image of the galaxy (Image Credit & © Carnegie-Irvine Galaxy Survey; used by permission)
Carnegie-Irvine Galaxy Survey image of spiral galaxy NGC 2935

NGC 2936 (= PGC 27422, and with
NGC 2937 = Arp 142), the Porpoise Galaxy
Discovered (Mar 3, 1864) by Albert Marth
A magnitude 13.1 spiral galaxy (type S? pec) in Hydra (RA 09 37 44.1, Dec +02 45 39)
Historical Identification: Per Dreyer, NGC 2936 (= GC 5497, Marth 175, 1860 RA 09 30 26, NPD 86 38) is "very faint, irregularly round". The position precesses to RA 09 37 42.2, Dec +02 44 24, about 1.4 arcmin south southwest of the galaxy listed above, the description fits and there is nothing nearby save for the companion (NGC 2937) observed by Marth on the same night, making the identification of both objects certain.
Physical Information: Based on a recessional velocity of 6850 km/sec (the average of its radial velocity of 6890 km/sec and its companion's radial velocity of 6810 km/sec), NGC 2936 is about 320 million light years away. Given that and its apparent size of 1.45 by 0.9 arcmin, it is about 135 thousand light years across. It has been severely distorted by its recent and undoubtedly still ongoing interaction with NGC 2937, which see for images. With that companion, it is used by the Arp Atlas as an example of material emanating from elliptical galaxies.

NGC 2937 (= PGC 27423, and with
NGC 2936 = Arp 142)
Discovered (Mar 3, 1864) by Albert Marth
A magnitude 13.7 elliptical galaxy (type E3?) in Hydra (RA 09 37 45.0, Dec +02 44 51)
Historical Identification: Per Dreyer, NGC 2937 (= GC 5498, Marth 176, 1860 RA 09 30 27, NPD 86 38) is "faint, small, like a nebulous star". The position precesses to RA 09 37 43.2, Dec +02 44 24, only 0.6 arcmin southwest of the galaxy listed above, the description fits and there is nothing nearby save for the companion (NGC 2936) observed by Marth on the same night, making the identification of both objects certain.
Physical Information: Based on a recessional velocity of 6850 km/sec (the average of its radial velocity of 6810 km/sec and its companion's radial velocity of 6890 km/sec), NGC 2937 is about 320 million light years away. Given that and its apparent size of 0.75 by 0.5 arcmin, it is about 70 thousand light years across. With its companion, it is used by the Arp Atlas as an example of material emanating from elliptical galaxies.
SDSS image of region near peculiar spiral galaxy NGC 2936 and elliptical galaxy NGC 2937, which comprise Arp 142
Above, a 12 arcmin wide SDSS image centered on NGC 2936 and 2937, which comprise Arp 142
Below, a 1.5 arcmin wide image of Arp 142 (Image Credit NASA, ESA, & Hubble Heritage Team (STScI/AURA))
HST image of peculiar spiral galaxy NGC 2936 and elliptical galaxy NGC 2937, which comprise Arp 142

The Curious Incident In The Night: A Celestial Mystery

     On the night of April 2, 1801 William Herschel made a sweep (his 1096th) of the sky, apparently in his usual manner, but all fifteen objects observed on that night suffered from large errors in their positions which made identification of NGC entries based on his observations difficult or impossible. As a result, in the early 1900's Dreyer asked the Astronomer Royal to take photographic plates of the region involved, from which accurate positions were determined for 40 nebulae, including all of Herschel's objects. The resulting corrections in Herschel's positions were listed by Dreyer in notes to the 1912 publication The Scientific Papers of Sir William Herschel, and in a separate summary of all the errors of importance for NGC entries that Dreyer had found in going over Herschel's papers. But although the question of what Herschel observed had been solved, the cause of the error remained a mystery until Wolfgang Steinicke did a reevaluation of Herschel's work in 2011-12. Namely, on the night in question Herschel must have accidentally aligned his telescope 7 degrees away from the meridian. When his sister Caroline reduced his measurements she presumed that the telescope was (as usual) aligned to the meridian, making the calculated positions of the objects badly askew. A reduction of the original measurements corrected for the 7 degree error in azimuth yields positions that more nearly match the correct celestial positions, verifying Steinicke's conclusion and Dreyer's corrected positions. Readers can see the details of the story at the entry for NGC 3752 on Corwin's page of Notes for NGC objects. A discussion of the effect on identification of individual objects accompanies (or will soon accompany) my NGC entries for each of the objects in question, as shown in the following list:

Objects Affected By The Error
WH I 282 - 284 (= NGC 2977, 3183 and 3329)
WH II 903 - 905 (= NGC 3061, 3523 and 3752)
WH III 963 - 971 (= NGC 2938, 3144, 3155, 3197, 3465, 3500, 3747?, 3901 and 3939)

NGC 2938 (= PGC 27473)
Discovered (Apr 2, 1801) by
William Herschel
Supposedly but not observed (Apr 5, 1832) by John Herschel
A magnitude 13.5 spiral galaxy (type SB(rs)cd?) in Draco (RA 09 38 24.9, Dec +76 19 09)
(JH observed a magnitude 14.4 star at RA 09 45 18.5, Dec +76 33 49)
Historical Identification: Per Dreyer, NGC 2938 (= GC 1883 = JH 612 = WH III 963?, 1860 RA 09 30 28, NPD 12 47.8) is "extremely faint, small, irregular figure, double star 3 arcmin to east". The position precesses to RA 09 45 24.8, Dec +76 34 08, in a completely stellar region about half an arcmin northeast of the star listed above. There is confusion about this identification due to the fact that the first part of the description ("extremely faint, small, irregular figure") corresponds to William Herschel's III 963, which is a completely different object (as discussed below), and only the position and the note about the double star are related to John Herschel's #612. Dreyer's 1912 revision of NGC entries based on a reassessment of William Herschel's observations should have cleared up the matter, but unfortunately it was phrased in a way that specifically states that NGC 2938 is a star, and the 3 arcmin distance between the star listed above and the double star to its east appears to make its identification as NGC 2938 certain.
     Whether the preceding is correct depends on how what Dreyer wrote in 1912 is interpreted, so a brief review of the history behind that entry is in order. As noted in the discussion of the problems caused by William Herschel's misalignment of his telescope on Apr 2, 1801 (shown above), all the objects observed by Herschel on that evening had large errors in their position that made their identification difficult or impossible. As a result, when John Herschel tried to observe his father's III 963 he used a completely wrong position and ended up mistaking the star listed above for what his father observed. Even at the time that Dreyer published the NGC he must have had doubts about the accuracy of John Herschel's identification of his #612 with his father's III 963, as shown by the question mark he must have added to the elder Herschel's entry (since that question mark did not appear in the GC). And when Dreyer was undertaking the reassessment of William Herschel's work that was published in The Scientific Papers of Sir William Herschel he felt sufficiently certain that there was something very wrong with all the observations done on Apr 2, 1801 that he asked the Astronomer Royal to take photographic plates of the regions observed by Herschel on that evening. As a result, a 1911 paper published by the Royal Greenwich Observatory gives accurate positions for 40 nebulae in that region (including all the objects observed by the elder Herschel), and in his 1912 summary of revisions to the NGC Dreyer stated "(NGC) 2938 is not III 963 (only a star on Greenwich plate). The place of III 963 is (1860 RA) 09 23 27, (NPD) 13 03.6."
     Here we come to the heart of the problem. Since the GC and NGC were supposed to be catalogs of clusters and nebulae, when Dreyer found that the original NGC position for 2938 was only a star and the nebula described in the GC entry had a completely different position, his usual practice would have led to a statement similar to "2938: NGC position is only a star; per Greenwich plate the position is 09 23 27, 13 03.6 (= WH III 963)". And if he had written his revision in that way there would be no doubt that NGC 2938 = WH III 963 = PGC 27473, because the position given in the correction falls exactly on the galaxy listed above (after precessing to current coordinates). But that is not what Dreyer's note says. It says that NGC 2938 is not III 963, but merely a star. In other words, NGC 2938 is the star observed by John Herschel, and William Herschel's nebula, though it might be more deserving of an NGC entry, is left out in the cold. As a result, in an earlier iteration of this entry I stated that NGC 2938 must be the star and not the galaxy. However, everyone else interprets Dreyer's note in the more usual way, taking it to mean that the earlier position of NGC 2938 was merely that of a star, and the correct position was that of William Herschel's nebula. One could easily have a lengthy quasi-medieval argument about whether Dreyer wrote what he meant or meant what he wrote, but there is no doubt that (far more deservedly) NGC 2938 will continue to be identified as the galaxy, and not the star.
Physical Information: Based on a recessional velocity of 2285 km/sec, PGC 27473 is about 105 million light years away, in good agreement with redshift-independent distance estimates of 100 to 180 million light years. Given that and its apparent size of 1.7 by 0.9 arcmin, it is about 50 thousand light years across.
DSS image of region near the star that is Dreyer's NGC 2938
Above, a 12 arcmin wide DSS image centered on the star that is Dreyer's NGC 2938
Below, a 12 arcmin wide DSS image centered on the galaxy universally accepted as NGC 2938
DSS image of region near PGC 27473, the spiral galaxy that is listed as NGC 2938
Below, a 2 arcmin wide DSS image of the galaxy
DSS image of spiral galaxy PGC 27473, which is universally identified as NGC 2938

NGC 2939 (= PGC 27451)
Discovered (Jan 18, 1784) by
William Herschel
Also observed (Jan 18, 1828) by John Herschel
A magnitude 12.4 spiral galaxy (type Sbc? pec) in Leo (RA 09 38 07.9, Dec +09 31 26)
Historical Identification: Per Dreyer, NGC 2939 (= GC 1884 = JH 614 = WH III 4, 1860 RA 09 30 39, NPD 79 51.5) is "very faint, small, very little extended, brighter middle, triple star to northeast". The position precesses to RA 09 38 08.5, Dec +09 30 51, within the southern outline of the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 3340 km/sec, NGC 2939 is about 155 million light years away, in good agreement with redshift-independent distance estimates of 125 to 175 million light years. Given that and its apparent size of 3.35 by 0.75 arcmin (including an extended arm on its northern side, whence the addition of "pec" to its type), it is about 150 thousand light years across.
SDSS image of region near spiral galaxy NGC 2939, also showing NGC 2940 and IC 548
Above, a 12 arcmin wide SDSS image centered on NGC 2939, also showing NGC 2940 and IC 548
Below, a 2.8 by 3.4 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2939

NGC 2940 (= PGC 27448)
Discovered (1877) by
Wilhelm Tempel
A magnitude 13.6 lenticular galaxy (type E/S0?) in Leo (RA 09 38 05.2, Dec +09 37 00)
Historical Identification: Per Dreyer, NGC 2940 (Tempel list I (#25), 1860 RA 09 30 39, NPD 79 46.5) is "very faint, small, 5 arcmin north of h614", h614 being NGC 2939. The position precesses to RA 09 38 08.7, Dec +09 35 51, about 1.4 arcmin southeast of the galaxy listed above, the description fits (including the position relative to NGC 2939) and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 8620 km/sec, a straightforward calculation indicates that NGC 2940 is about 400 million light years away, in poor agreement with a single redshift-independent distance estimate of 135 million light years, which is obviously well off the mark. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 390 million light years away at the time the light by which we see it was emitted, about 395 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.9 by 0.8 arcmin, it is about 100 thousand light years across.
SDSS image of region near spiral galaxy NGC 2940, also showing NGC 2939
Above, a 12 arcmin wide SDSS image centered on NGC 2940, also showing NGC 2939
Below, a 1.2 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2940

NGC 2941 (= PGC 27470)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 15.0 lenticular galaxy (type (R)S0(r)a?) in Leo (RA 09 38 24.2, Dec +17 02 40)
Historical Identification: Per Dreyer, NGC 2941 (= GC 5499, Marth 177, 1860 RA 09 30 39, NPD 72 19) is "extremely faint, very small, a little extended, western of 2", the other being NGC 2943. The position precesses to RA 09 38 24.0, Dec +17 03 20, about 0.7 arcmin north of the galaxy listed above, the description fits (especially the position relative to NGC 2943) and there is nothing comparable nearby save for the aforementioned NGC 2943, so the identification is certain.
Physical Information: Based on a recessional velocity of 7360 km/sec, a straightforward calculation indicates that NGC 2941 is between 340 and 345 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was between 330 and 335 million light years away at the time the light by which we see it was emitted, between 335 and 340 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.5 by 0.4 arcmin, the galaxy is about 50 thousand light years across.
SDSS image of region near lenticular galaxy NGC 2941, also showing NGC 2943
Above, a 12 arcmin wide SDSS image centered on NGC 2941, also showing NGC 2943
Below, a 0.8 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2941

NGC 2942 (= PGC 27527)
Discovered (Mar 6, 1828) by
John Herschel
A magnitude 12.6 spiral galaxy (type SA(s)bc?) in Leo Minor (RA 09 39 08.0, Dec +34 00 23)
Historical Identification: Per Dreyer, NGC 2942 (= GC 1885 = JH 613, 1860 RA 09 30 43, NPD 55 21.9) is "faint, pretty large, very little extended 0°, very gradually a little brighter middle". The position precesses to RA 09 39 08.8, Dec +34 00 24, right on the galaxy listed above, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 4425 km/sec, NGC 2942 is about 205 million light years away, in reasonable agreement with redshift-independent distance estimates of 140 to 200 million light years. Given that and its apparent size of 2.2 by 1.8 arcmin, it is about 130 thousand light years across.
SDSS image of region near spiral galaxy NGC 2942
Above, a 12 arcmin wide SDSS image centered on NGC 2942
Below, a 2.4 by 2.6 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2942

NGC 2943 (= PGC 27482)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 12.4 elliptical galaxy (type E5?) in Leo (RA 09 38 32.9, Dec +17 01 53)
Historical Identification: Per Dreyer, NGC 2943 (= GC 5500, Marth 178, 1860 RA 09 30 47, NPD 72 20) is "faint, small, irregularly round, brighter middle, eastern of 2", the other being NGC 2941. The position precesses to RA 09 38 31.9, Dec +17 02 19, on the northern rim of the galaxy listed above, the description fits and there is nothing comparable nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 8375 km/sec, a straightforward calculation indicates that NGC 2943 is about 390 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was between 375 and 380 million light years away at the time the light by which we see it was emitted, between 380 and 385 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 2.2 by 1.1 arcmin, the galaxy is about 240 thousand light years across.
SDSS image of region near lenticular galaxy NGC 2943, also showing NGC 2943
Above, a 12 arcmin wide SDSS image centered on NGC 2943, also showing NGC 2941
Below, a 3 arcmin wide SDSS image of the galaxy
SDSS image of lenticular galaxy NGC 2943

NGC 2944 (= PGC 27533 + PGC 27534, and = all or most of
Arp 63)
Discovered (Mar 27, 1886) by Johann Palisa
A pair of interacting galaxies in Leo
PGC 27533 = A magnitude 14.0 spiral galaxy (type SB(s)c pec?) at RA 09 39 18.0, Dec +32 18 39
PGC 27534 = A magnitude 14.8 spiral galaxy (type SB? pec?) at RA 09 39 16.8, Dec +32 18 38
Historical Identification: Per Dreyer, NGC 2944 (Palisa (#3), 1860 RA 09 30 57, NPD 57 03.7) is "faint, very small, a little brighter middle". The position precesses to RA 09 39 18.0, Dec +32 18 34, barely south of the nucleus of PGC 27533, so the identification is certain. The only question is which of that galaxy's companions should be included in the NGC listing; the decision made here to only include the brighter galaxies as part of NGC 2944 is based on the fact that PGC 27534 is less than a magnitude fainter than PGC 27533, but PGC 1990710 is three magnitudes fainter, so although Palisa's description can be reasonably interpreted to include both of the brighter galaxies, the faintest one was undoubtedly beyond the reach of his telescope.
Discovery Notes: Corwin notes that there is a considerably brighter pair of galaxies (PGC 27546 and 27547, which comprise Arp 129) only 3 arcmin north of the triple listed here, and to be sure that the NGC entry correctly represents what Palisa recorded, he did a recalculation of Palisa's micrometrically measured position. The result falls only 3 arcsec from the center of PGC 27533, so although it's odd that Palisa saw the fainter group and missed the brighter one, there is no doubt that the identification given here is correct.
Physical Information: NGC 2944 is a complex structure consisting of a fairly large spiral galaxy (PGC 27533) and a smaller one (PGC 27534) which is almost certainly physically interacting with it on its western side. It is also associated with a third object (PGC 1990710) on its southeastern side. Based on a recessional velocity of 6800 km/sec, NGC 2944 is about 315 million light years away. Given that, the 0.75 by 0.25 arcmin apparent size of its main component corresponds to about 70 thousand light years, while the 0.45 by 0.15 arcmin size of its western component (including its western "tail") corresponds to about 40 thousand light years. The pair (or perhaps even the group) of galaxies is used by the Arp Atlas as an example of a spiral galaxy with high surface brightness companions. Whether that means that Arp 63 includes only the two brighter galaxies or also includes the much fainter one is not clear, because Arp had no notes about the object in his catalog; but although certainly not part of NGC 2944 and perhaps not even part of Arp 63, PGC 1990710's obvious interaction with NGC 2944 means it is worthy of discussion (immediately below).
SDSS image of region near spiral galaxy NGC 2944 and its apparent companion, PGC 1990710, some combination of which comprises Arp 63
Above, a 12 arcmin wide SDSS image centered on NGC 2944, also showing PGC 1990710
Below, a 1.4 arcmin wide SDSS image of the trio
SDSS image of spiral galaxy NGC 2944 and its apparent companion, PGC 1990710, some combination of which comprises Arp 63
Below, a 12 arcmin wide region centered on NGC 2944, also showing PGC 27546 and 27547
SDSS image of region near spiral galaxy NGC 2944 and its apparent companion, PGC 1990710, some combination of which comprises Arp 63; also shown are PGC 27546 and 27547

PGC 1990710 (perhaps, as a companion of
NGC 2944, a part of Arp 63)
Not an NGC object, but listed here due to its association with NGC 2944
A magnitude 17(?) galaxy (type SB? pec) in Leo (RA 09 39 19.7, Dec +32 18 21)
Physical Information: (Listed in NED as NGC 2944 NED02, and as Arp 63 NED02.) PGC 1990710's recessional velocity of 6725 km/sec is close enough to that of NGC 2944 (which see for images) that even without their apparent interaction we might suspect that they are related. Given that, its distance is probably the same approximately 315 million light years, and its apparent size of 0.3 by 0.15 arcmin corresponds to about 25 to 30 thousand light years. As noted in the entry for NGC 2944, whether Arp meant to include PGC 1990710 as part of Arp 63 is unknown, as that is supposed to represent a spiral galaxy with a high surface brightness companion, which certainly includes the two components of NGC 2944, but is far less likely to include their much fainter southeastern companion, and Arp did not add any note for the object that might have made his intentions clear.

NGC 2945 (= PGC 27418)
Discovered (Jan 23, 1835) by
John Herschel
A magnitude 12.1 lenticular galaxy (type E/SA0?) in Hydra (RA 09 37 41.1, Dec -22 02 06)
Historical Identification: Per Dreyer, NGC 2945 (= GC 1886 = JH 3180, 1860 RA 09 31 16, NPD 111 24.9) is "faint, small, round, gradually a little brighter middle, 2 or 3 small stars near". The position precesses to RA 09 37 42.0, Dec -22 02 33, just off the southeastern rim of the galaxy listed above, the description is reasonable and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 4630 km/sec, NGC 2945 is about 215 million light years away, in fair agreement with redshift-independent distance estimates of 230 to 300 million light years. Given that and its apparent size of 1.4 by 1.3 arcmin, it is 85 to 90 thousand light years across.
DSS image of region near lenticular galaxy NGC 2945
Above, a 12 arcmin wide DSS image centered on NGC 2945
Below, a 1.8 arcmin wide DSS image of the galaxy
DSS image of lenticular galaxy NGC 2945

NGC 2946 (= PGC 27521)
Discovered (Apr 1, 1864) by
Albert Marth
A magnitude 14.0 spiral galaxy (type SBb? pec) in Leo (RA 09 39 01.6, Dec +17 01 31)
Historical Identification: Per Dreyer, NGC 2946 (= GC 5501, Marth 179, 1860 RA 09 31 16, NPD 72 20) is "very faint, small, extended". The position precesses to RA 09 39 00.8, Dec +17 02 16, only 0.8 arcmin north of the center of the galaxy listed above and just west of its northern outline, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 8955 km/sec, a straightforward calculation indicates that NGC 2946 is about 415 million light years away, in fair agreement with redshift-independent distance estimates of 445 to 470 million light years. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 405 million light years away at the time the light by which we see it was emitted, about 410 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 1.6 by 0.5 arcmin, the galaxy is about 190 thousand light years across.
SDSS image of region near spiral galaxy NGC 2946
Above, a 12 arcmin wide SDSS image centered on NGC 2946
Below, a 1.8 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2946

NGC 2947 (= PGC 27309 =
IC 547 = IC 2494)
Discovered (May 6, 1886) by Francis Leavenworth (and later listed as NGC 2947)
Discovered (Apr 20, 1892) by Stephane Javelle (and later listed as IC 547)
Discovered (Feb 20, 1898) by Lewis Swift (and later listed as IC 2494)
A magnitude 12.1 spiral galaxy (type SAB(rs)bc?) in Hydra (RA 09 36 05.8, Dec -12 26 12)
Historical Identification: Per Dreyer, NGC 2947 (Leavenworth list I (#156), 1860 RA 09 31 35, NPD 101 48.0) is "extremely faint, pretty large, irregularly round, gradually brighter middle". The position precesses to RA 09 38 21.5, Dec -12 25 43, but there is nothing in the completely stellar field near that position. However, it is common knowledge that observations at the Leander McCormick Observatory were often in error by a minute or more of right ascension, and there is a suitable candidate for Leavenworth's #156 just over two minutes to the west, so the galaxy listed above is generally accepted as being NGC 2947.
Discovery Notes: Despite the current recognition of PGC 27309 as NGC 2947, the fact that its position was poorly recorded inevitably led to later observations of the same object as apparently "new" discoveries, hence its also being listed as IC 547, and thanks to an oversight by Swift and Dreyer, also as IC 2494 (which, as noted by Corwin, makes PGC 27309 the only object listed in all three of Dreyer's catalogs).
Physical Information: Based on a recessional velocity of 2805 km/sec, NGC 2947 is about 130 million light years away. Given that and its apparent size of 2.0 by 1.25 arcmin, it is about 75 thousand light years across.
DSS image of region near spiral galaxy NGC 2947, also known as IC 547 and IC 2494
Above, a 12 arcmin wide DSS image centered on NGC 2947
Below, a 2.1 arcmin wide image of the galaxy (Image Credit & © Carnegie-Irvine Galaxy Survey; used by permission)
Carnegie-Irvine Galaxy Survey image of spiral galaxy NGC 2947, also known as IC 547 and IC 2494

NGC 2948 (= PGC 27518)
Discovered (Mar 24, 1786) by
William Herschel
Also observed (Dec 25, 1827) by John Herschel
A magnitude 12.9 spiral galaxy (type SBbc?) in Leo (RA 09 38 59.2, Dec +06 57 20)
Historical Identification: Per Dreyer, NGC 2948 (= GC 1887 = JH 615 = WH III 519, 1860 RA 09 31 35, NPD 82 24.0) is "very faint, pretty large, very gradually brighter middle". The position precesses to RA 09 38 59.4, Dec +06 58 15, only 0.9 arcmin north of the center of the galaxy listed above and even closer to its northern boundary, the description fits and there is nothing else nearby so the identification is certain.
Physical Information: Based on a recessional velocity of 4985 km/sec, NGC 2948 is about 230 million light years away, in good agreement with redshift-independent distance estimates of 160 to 250 million light years. Given that and its apparent size of 1.6 by 0.7 arcmin, it is about 105 thousand light years across.
SDSS image of region near spiral galaxy NGC 2948
Above, a 12 arcmin wide SDSS image centered on NGC 2948
Below, a 1.8 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy NGC 2948

NGC 2949 (= PGC 27579 (= PGC 1516936 + "PGC 5067067"))
Discovered (Apr 1, 1864) by
Albert Marth
A pair of lenticular galaxies in Leo (RA 09 39 56.2, Dec +16 47 10)
PGC 1516936 = A magnitude 14.4 lenticular galaxy (type S0?) at RA 09 39 55.2, Dec +16 47 06
"PGC 5067067" = A magnitude 16(?) lenticular galaxy (type S0?) at RA 09 39 57.3, Dec +16 47 13
Historical Identification: Per Dreyer, NGC 2949 (= GC 5502, Marth 180, 1860 RA 09 32 09, NPD 72 35) is "very faint, double?". The position precesses to RA 09 39 53.1, Dec +16 47 10, less than half an arcmin west of the western member of the pair listed above, the description fits and there is nothing comparable nearby so the identification is certain. (Despite that, some references list PGC 27573 as NGC 2949, so it is discussed immediately below).
Physical Information: As shown in the following paragraphs, the fainter eastern component's recessional velocity suggests that it is about 15 million light years closer to us than its apparent companion, but peculiar (non-Hubble expansion) velocities can exceed the difference in their recessional velocities, so the pair may be physical companions nearer the average of the distances shown below (namely, about 630 to 635 million light years). However, the lack of any obvious interaction between the two means they are not as close as they appear, and since it is possible that the 15 million light year separation is real, I treat them below as completely separate objects.
     Based on a recessional velocity of 14555 km/sec, a straightforward calculation indicates that PGC 1516936 is 675 to 680 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 640 million light years away at the time the light by which we see it was emitted, about 655 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.55 by 0.3 arcmin, the galaxy is about 100 thousand light years across.
     The fainter component is listed in LEDA as galaxy PGC 5067067, but that designation is not recognized by a search of the LEDA database; instead, it is listed as NPM1G+17.0270. Based on a recessional velocity of 14170 km/sec, a straightforward calculation indicates that "PGC 5067067" is about 660 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 625 million light years away at the time the light by which we see it was emitted, about 640 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.3 by 0.2 arcmin, the galaxy is about 55 thousand light years across.
SDSS image of region near the pair of lenticular galaxies listed as NGC 2949
Above, a 12 arcmin wide SDSS image centered on NGC 2949
Below, a 1.2 arcmin wide SDSS image of the pair
SDSS image of the pair of lenticular galaxies listed as NGC 2949

PGC 27573 (not =
NGC 2949)
Not an NGC object but listed here since sometimes misidentified as NGC 2949
A magnitude 15(?) spiral galaxy (type SAB(rs)b? pec) in Leo (RA 09 39 52.2, Dec +16 55 05)
Historical Misidentification: This galaxy was misidentified as NGC 2949 in the 1973 RNGC by Sulentic and Tifft, and even though it is 8 arcmin from the correct location and not as bright as the correct object, it is still misidentified as the NGC object in several places.
Physical Information: Based on a recessional velocity of 14330 km/sec, a straightforward calculation indicates that PGC 27573 is about 665 million light years away. However, for objects at such distances we should take into account the expansion of the Universe during the time it took their light to reach us. Doing that shows that the galaxy was about 630 million light years away at the time the light by which we see it was emitted, about 645 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.95 by 0.6 arcmin (including its fainter outer regions), the galaxy is about 175 thousand light years across.
SDSS image of region near spiral galaxy PGC 27573, which is sometimes misidentified as NGC 2949
Above, a 12 arcmin wide SDSS image centered on PGC 27573
Below, a 1 arcmin wide SDSS image of the galaxy
SDSS image of spiral galaxy PGC 27573, which is sometimes misidentified as NGC 2949
Below, a 12 arcmin wide SDSS image showing PGC 27573 and the correct NGC 2949
SDSS image of region between spiral galaxy PGC 27573, which is sometimes misidentified as NGC 2949, and the pair of galaxies that is the correct NGC 2949
Celestial Atlas
(NGC 2850 - 2899) ←     NGC Objects: NGC 2900 - 2949     → (NGC 2950 - 2999)