Historical Identification: Per Dreyer, NGC 4800 (= GC 3305 = JH 1478 = WH I 211, 1860 RA 12 48 11, NPD 42 42.7) is "pretty bright, considerably small, round, pretty suddenly brighter middle, 14th magnitude star preceding (to west)." The position precesses to RA 12 54 36.8, Dec +46 31 42, on the southwestern rim of the nucleus of the galaxy listed above and well within its overall outline, the description fits and there is nothing else nearby, so the identification is certain.
Discovery Note: Per Gottlieb, d'Arrest noted and measured the positions of the 13th magnitude stars 4.7 sec of RA preceding and 19.6 sec of RA following (and a little south), which helps confirm the identification, hence my addition of d'Arrest's observation.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1085 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4800 is about 50 million light-years away, in good agreement with redshift-independent distance estimates of about 50 to 95 million light-years. Given that and its apparent size of about 1.85 by 1.4 arcmin (from the images below), the galaxy is about 25 to 30 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4801 (= GC 3306 = JH 1479 = WH III 816, 1860 RA 12 48 27, NPD 36 08.5) is "extremely faint, small, a little extended." The position precesses to RA 12 54 40.9, Dec +53 05 55, less than 0.7 arcmin northeast 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 relative to the Cosmic Background Radiation of 16380 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4801 is about 760 to 765 million light-years away, in good agreement with a single redshift-independent distance estimate of about 770 to 775 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 715 million light-years away at the time the light by which we see it was emitted, about 735 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 about 0.8 by 0.6 arcmin (from the images below), the galaxy is about 165 thousand light-years across.
Possible Companion: Corwin notes a possible companion (SDSS J12543922+5305191) at RA 12 54 39.2, Dec +53 05 19, but other than its position, brightness (roughly magnitude 20) and apparent size (about 0.05 arcmin, from the images below), nothing is known about the object, so whether it is an actual companion or merely an optical double is unknown.

Historical Identification: Per Dreyer, NGC 4802 (Tempel list V (#21), 1860 RA 12 48 29, NPD 101 17.7) is "very faint, small, 10th magnitude star attached." The second IC adds "Not found by Howe (one night). The description agrees with that of 4804, exactly 1 degree south. Tempel says it is 8 seconds following Lamont 1234 (10th magnitude), but this identification may be wrong". The position precesses to RA 12 55 48.0, Dec -12 03 16, on the western edge of the galaxy listed above, Tempel's description fits and there is nothing else nearby, so the identification is certain. (For a discussion of the duplicate entry, see NGC 4804.)
Discovery Note: Howe supposedly found NGC 4804 at the NGC position but could not find 4802, and surmised that they might be the same if the position of 4802 was off by 1 degree, but it is actually the position of 4804 that is off by a degree! A very odd mistake for Howe to have made, as his positions were usually very accurate.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1275 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4802 is about 60 million light-years away, in poor agreement with two redshift-independent distance estimates of about 35 to 40 million light-years. Using the Hubble Flow distance and its apparent size of about 2.3 by 1.75 arcmin (from the images below), the galaxy is about 40 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4803 (= GC 5680, Marth #245, 1860 RA 12 48 31, NPD 81 00) is "extremely faint, extremely small, round, a little brighter middle." The position precesses to RA 12 55 34.9, Dec +08 14 26, only 0.3 arcmin due east 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 relative to the Cosmic Microwave Background radiation of 2965 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4803 is about 135 to 140 million light-years away. Given that and its apparent size of about 0.65 by 0.45 arcmin (from the images below), the galaxy is about 25 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4804 (= GC 3307 = WH IV 40, 1860 RA 12 48 34, NPD 102 17.6) is "small, attached to pretty bright star." The position precesses to RA 12 55 53.8, Dec -13 03 10, about 0.8 arcmin due south of a double star that is often listed as NGC 4804, but in no way resembles Herschel's description; and as noted in the entry for NGC 4802, Dreyer stated that the description (perfectly) matches that of Tempel's object, so it appears certain that Herschel simply made a one-digit error in the declination, and NGC 4804 is an earlier but misrecorded observation of NGC 4802. (Altering Herschel's NPD by exactly 1 degree yields a place less than 0.9 arcmin nearly due east of NGC 4802, and its appearance is a good match for Herschel's description, so the duplicate entry is essentially certain. For a discussion of Howe's observation, see NGC 4802.)
Discovery Note: Gottlieb states that Harold Knox-Shaw was the first to propose that NGC 4802 and 4804 are the same, in 1912-14; but since Howe proposed that in 1900, and Dreyer mentioned Howe's proposal in the (May, 1908) IC2, Knox-Shaw was not the first, after all.
Note About The Identification: LEDA, NED and Corwin either confirm or indicate a preference for the identification of NGC 4804 as a duplicate entry for NGC 4802, but Steinicke lists the object as the double star, and Corwin reluctantly admits that as a possibility; however, given Herschel's description and his keen eye, I cannot accept the identification as the double star; so its entry immediately below is meant to serve only as a warning.
Physical Information: Given the essentially certain duplicate entry, see NGC 4802 for anything else.

Historical Misidentification: As noted in the entry for NGC 4804, although that is almost certainly a misrecorded observation of NGC 4802, there is a minority-opinion (mis?)identification of the entry as the double star less than an arcminute to the north of Herschel's position. Since his description is nothing like what he would have recorded if he had observed the double star (namely, there is no 'pretty bright' star anywhere near, let alone 'attached' to the double star), the main purpose of this entry is to serve as a warning about the almost certain misidentification.
Addendum Per Corwin: Although Corwin feels that NGC 4804 is almost certainly a duplicate of NGC 4802, he notes that none of the other objects discovered by Herschel on the night in question had any obvious problems with their position, and that Herschel's detailed description, "Suspected a pretty bright star, with a seeming brush to the northwest may be a small nebula close to it, but there was no time to verify it," could refer to the double star, since the northwestern star is the fainter of the pair, and could have been mistaken for "a seeming brush", providing that one presumes that a 13th magnitude star would be classified as "pretty bright"; hence his cautious supposition that the double star might be what Herschel observed. My objection is that even with Herschel's 18.7-inch speculum, a 13th magnitude star would not be likely to be described as "pretty bright", and as already stated, in the end Corwin concludes that NGC 4804 is probably a 1-degree NPD error in an observation of the future NGC 4802.
Addendum: Gottlieb states that the double star near Herschel's position is "easily resolved... (about 20 arcsec separation)", thereby implying that if Herschel should have been able to see that it was a double star; though given Herschel's "no time to verify it" (quoted in full in the addendum about Corwin), it is conceivable that Herschel simply didn't observe it closely enough to tell what it was, whence the minority opinion that the double star is what Herschel observed.

Historical Identification: Per Dreyer, NGC 4805 (Bigourdan (list II #59), 1860 RA 12 48 38, NPD 61 15) is "very faint." The position precesses to RA 12 55 25.5, Dec +27 59 26, only about 0.6 arcmin northeast of the star listed above, and given the description and Bigourdan's typical accuracy, the fact that there is absolutely nothing else in the region, the identification is essentially certain. However, LEDA lists PGC 44030 as NGC 4805, and PGC 93687 is also sometimes misidentified as NGC 4805, so those objects are discussed in the following entries.
Discovery Note: Bigourdan wrote "Extremely faint nebulosity (mag 13.5), elusive in shape; within its extent there is a star of mag 13.4 - 13.5, but it is impossible to say what is its position in relation to the center of the nebulosity." As noted by Corwin, this suggests that the star itself was the source of the apparent nebulosity, and though the star above is fainter than Bigourdan's estimate, since there is absolutely nothing else near his position, and there were a number of cases in which Bigourdan mistook a star (or stars) as a faint nebulosity, it seems certain that this is simply another such case.
Addendum: Gottlieb notes that not only LEDA but also RNGC misidentified faint galaxies 2 and 3 arcmin southeast of the star as NGC 4805, so PGC 93687, which is presumably the RNGC misidentification, is also given an entry below.

Historical Misidentification: Presumably chosen as NGC 4805 simply because it is the closest galaxy to Bigourdan's position for NGC 4805, this object cannot be what he observed. It is far too faint for him to have seen, and there is no nearby star to satisfy his description of the object. However, since it is misidentified as NGC 4805 in some places, this entry serves as a warning about the error.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6500 km/sec (and H₀ = 70 km/sec/Mpc), PGC 44030 is about 300 to 305 million light-years away. Given that and its apparent size of about 0.21 by 0.19 arcmin (from the images below), the galaxy is about 18 thousand light-years across.

Historical Misidentification: Presumably chosen as NGC 4805 simply because it is the brightest galaxy anywhere near Bigourdan's position for NGC 4805, this object cannot be what he observed. It is too faint for him to have seen, and there is no nearby star to satisfy his description of the object. However, since it is misidentified as NGC 4805 in some places, this entry serves as a warning about the error.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 26155 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 93687 is about 1215 to 1220 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 1100 million light-years away at the time the light by which we see it was emitted, about 1145 to 1150 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 about 0.4 by 0.15 arcmin (from the images below), the galaxy is about 125 to 130 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4806 (= GC 3308 = JH 3440, 1860 RA 12 48 39, NPD 118 45.0) is "faint, considerably small, round, gradually a very little brighter middle." The position precesses to RA 12 56 12.9, Dec -29 30 33, barely outside the southern 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 relative to the Cosmic Microwave Background radiation of 2720 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4806 is about 125 to 130 million light-years away. Given that and its apparent size of about 1.25 by 1.05 arcmin (from the images below), the galaxy is about 45 to 50 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4807 (= GC 5681, d'Arrest, 1860 RA 12 48 40, NPD 61 43.2) is "faint, pretty small, round, brighter middle." The position precesses to RA 12 55 28.0, Dec +27 31 14, barely outside the western 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 relative to the Cosmic Background Radiation of 7260 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4807 is about 335 to 340 million light-years away, in good agreement with redshift-independent distance estimates of about 280 to 485 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 325 to 330 million light-years away at the time the light by which we see it was emitted, about 330 to 335 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 about 0.75 by 0.65 arcmin (from the images below), the galaxy is about 70 to 75 thousand light-years across.
Possible Companions?: Since the distances of NGC 4807 and PGC 214040 appear to be essentially the same, there is a good chance that they are physical companions.

Warning About Non-Standard Designation: There are no standards for assigning letters to NGC/IC objects, so using such letters can cause data belonging to one galaxy to be assigned to a completely different one. For that reason, such non-standard designations should never be used. In this case, the origin of the non-standard designation appears uncertain, but it does appear in SIMBAD, which though it contains an almost infinite number of errors, is a "standard" database, hence the importance of this warning.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7295 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 214040 is about 340 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 330 million light-years away at the time the light by which we see it was emitted, about 335 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 about 0.35 by 0.15 arcmin for the brighter part of the galaxy and about 0.6 by 0.35 arcmin for its faint halo (from the images below), the galaxy is about 30 to 35 thousand light-years across and its halo spans about 55 to 60 thousand light-years.
Possible Companion?: Since the distances of NGC 4807 and PGC 214040 appear to be essentially the same, there is a good chance that they are physical companions.

Historical Identification: Per Dreyer, NGC 4808 (= GC 3311 = JH 1480 = WH I 141, 1860 RA 12 48 43, NPD 84 56.0) is "pretty bright, considerably large, extended 135°±." The position precesses to RA 12 55 49.8, Dec +04 18 26, on the northeastern 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 relative to the Cosmic Microwave Background radiation of 1085 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4808 is about 50 million light-years away, in good agreement with redshift-independent distance estimates of about 50 to 75 million light-years. Given that and its apparent size of about 2.6 by 0.9 arcmin for the main galaxy and about 3.2 by 1.9 arcmin counting the faint clockwise northwestern and southeastern spiral arms (from the images below), the main galaxy is about 35 to 40 thousand light-years across and the entire structure spans about 45 to 50 thousand light-years.

Historical Identification: Per Dreyer, NGC 4809 and 4810 (= GC 3309 and 3310, 4th Lord Rosse, 1860 RA 12 48 45, NPD 86 42±) are "faint, a double nebula, extended at right angles to each other." The position precesses to RA 12 55 53.1, Dec +02 32 26, but there is nothing there. The problem is that Mitchell wrote "Found in looking for h 1509 and at 12h 48m.5± and a little north of h 1509 a faint double nebula," and Dreyer naturally assumed that "a little north" literally meant that, whereas the pair of galaxies which clearly fits Mitchell's description is nearly 9 arcmin north of JH 1509 (= NGC 4900). The galaxies are also a minute of time further west than Mitchell's position, but the ± in Mitchell's RA makes that not at all unreasonable, and there is nothing else anywhere near the field that remotely fits the description, so the identification of NGC 4809 and 4810 as the two galaxies shown in their entries is certain. (There is a slight bit of confusion involving their designations, as discussed in their Designation Notes, but given their irregular figures, that is hardly surprising.)
Discovery Note: Given the date of the observation shown in the paper published by the 4th Lord Rosse, he cannot have been the discoverer, who must have been one of the assistants of the former (3rd) Lord Rosse, and based on that date, must have been R. J. Mitchell.
Designation Note: Since the NGC is in order of right ascension, the western member of the pair should be NGC 4809, and the eastern member NGC 4810, but although the putative center of NGC 4809 is very slightly east of the center of NGC 4810 the galaxies have always been listed in the reverse order; and after more than a century, changing the designations because of a difference of less than a tenth of a minute of time would be confusing, so the oddity is universally ignored.
Addendum: Gottlieb notes that most catalogs list the northern component as NGC 4809 and the southern one as NGC 4810, but that UGC reverses the identifications and makes an error of +1 minute of time in their RA. He also notes that [presumably due to confusion about which galaxy is which NGC object] data recorded for one galaxy (size, position angle and magnitudes) often applies to the other one; so in my assessment of their nature I have carefully compared their appearance to their data, to try to ensure that their Physical Information is correctly applied.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1245 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4809 is about 55 to 60 million light-years away, in good agreement with redshift-independent distance estimates of about 45 to 75 million light-years, and consistent with the idea that it is a physical pair with NGC 4810. Given that and its apparent size of about 1.65 by 0.55 arcmin (from the images below), the galaxy is about 25 to 30 thousand light-years across.
Use By The Arp Atlas: With NGC 4810, NGC 4809 is used by The Arp Atlas of Peculiar Galaxies as an example of interacting galaxies, with the note "Resolution of knots."

Historical Identification: Per Dreyer, NGC 4809 and 4810 (= GC 3309 and 3310, 4th Lord Rosse, 1860 RA 12 48 45, NPD 86 42±) are "faint, a double nebula, extended at right angles to each other." As noted in the entry for NGC 4809, there is absolutely nothing at the NGC position, but that is due to Mitchell's note (quoted and discussed in the preceding entry) not giving Dreyer a very good idea of the actual location of the objects, and as stated there, the identification of NGC 4810 and 4809 with the galaxies shown here is certain. (There is a slight bit of confusion involving their designations, as discussed in their Designation Notes, but given their irregular figures, that is hardly surprising.)
Discovery Note: Given the date of the observation shown in the paper published by the 4th Lord Rosse, he cannot have been the discoverer, who must have been one of the assistants of the former (3rd) Lord Rosse, and based on that date, must have been R. J. Mitchell.
Designation Note: Since the NGC is in order of right ascension, the western member of the pair should be NGC 4809, and the eastern member NGC 4810, but although the putative center of NGC 4809 is very slightly east of the center of NGC 4810 the galaxies have always been listed in the reverse order; and after more than a century, changing the designations because of a difference of less than a tenth of a minute of time would be confusing, so the oddity is universally ignored.
Addendum: Gottlieb notes that most catalogs list the northern component as NGC 4809 and the southern one as NGC 4810, but that UGC reverses the identifications and makes an error of +1 minute of time in their RA. He also notes that [presumably due to confusion about which galaxy is which NGC object] data recorded for one galaxy (size, position angle and magnitudes) often applies to the other one; so in my assessment of their nature I have carefully compared their appearance to their data, to try to ensure that their Physical Information is correctly applied.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1240 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4910 is about 55 to 60 million light-years away, in reasonable agreement with a single redshift-independent distance estimate of about 70 million light-years, and consistent with the idea that it is a physical pair with NGC 4809. Given that and its apparent size of about 0.8 by 0.55 arcmin (from the images below), the galaxy is about 13 to 14 thousand light-years across.
Use By The Arp Atlas: With NGC 4809, NGC 4810 is used by The Arp Atlas of Peculiar Galaxies as an example of interacting galaxies, with the note "Resolution of knots."

Historical Identification: Per Dreyer, NGC 4811 (= GC 3312 = JH 3441, 1860 RA 12 49 06, NPD 131 02.3) is "extremely faint, considerably small, round, gradually brighter middle, preceding (western) of 2," the other being NGC 4812. The position precesses to RA 12 56 54.1, Dec -41 47 50, only about 0.3 arcmin due east of the center of the galaxy listed above and nearly within its outline, and the description and relative position of its companion make the identification certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 3530 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4811 is about 165 million light-years away, in fair agreement with a single redshift-independent distance estimate of about 145 to 150 million light-years. Given that and its apparent size of about 1.2 by 0.85 arcmin (from the images below), the galaxy is about 55 to 60 thousand light-years across. Despite their apparent proximity, the substantial difference in their recessional velocities probably means that NGC 4811 and 4812 are merely an optical double, and that NGC 4811 is about 20 million light-years closer to us.
Note About Classification: NGC 4811 is unusual in having two apparent axes of symmetry -- a brighter one slightly clockwise from north-south, and a fainter one a bit counter-clockwise from north-south -- and an extended envelope that is aligned more with the fainter axis than not. This makes assigning it a "type" difficult, and is why it is listed as a peculiar galaxy. LEDA lists it as merely SB0/a, presumably based on the brighter "bar", but NED lists two classifications -- SAB(rs)0/a, presumably assuming that the outer ringlike structure is due to some kind of spiral structure hidden by the poor quality of the available images, and SAB(rl)0/a, presumably suggesting that the ringlike structure is associated with the counter-clockwise linear structure. My decision to assign type (R')SB0/a? pec is based on the fact that the outer envelope is vaguely ringlike, but since the nature of the dual axis and outer envelope is not obvious, to just let "pec" represent all the peculiarities, along with this supplementary paragraph.

Historical Identification: Per Dreyer, NGC 4812 (= GC 3313 = JH 3442, 1860 RA 12 49 06, NPD 131 03.8) is "extremely faint, small, round, gradually brighter middle, following (eastern) of 2," the other being NGC 4811. The position precesses to RA 12 56 54.2, Dec -41 49 20, about 0.6 arcmin southeast of the center of the galaxy listed above, but the description and relative position of its companion make the identification certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 3945 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4812 is about 180 to 185 million light-years away. Given that and its apparent size of about 1.15 by 0.4 arcmin (from the images below), the galaxy is about 60 to 65 thousand light-years across. Despite their apparent proximity, the substantial difference in their recessional velocities probably means that NGC 4811 and 4812 are merely an optical double, and that NGC 4812 is about 20 million light-years further from us.

Historical Identification: Per Dreyer, NGC 4813 (= GC 3316 = JH 1482 = WH II 777, 1860 RA 12 49 20, NPD 96 03.5) is "faint, small, round, brighter middle." The position precesses to RA 12 56 35.1, Dec -06 49 02, on the western rim of the galaxy listed above, the description is a reasonable fit and there is nothing else nearby, so the identification is certain. (For a discussion of the possible duplication as IC 833, see that entry.)
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1730 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4813 is about 80 million light-years away. Given that and its apparent size of about 1.6 by 0.8 arcmin (from the images below), the galaxy is about 35 to 40 thousand light-years across. The galaxy is listed as a Seyfert galaxy (type Sy2) due to its exceptionally bright nucleus, and exhibits strong emission lines from highly excited gases.

Historical Identification: Per Dreyer, NGC 4814 (= GC 3315 = JH 1483 = WH I 243, 1860 RA 12 49 22, NPD 30 53.7) is "bright, pretty small, very little extended, very gradually brighter middle." The position precesses to RA 12 55 22.5, Dec +58 20 45, almost dead center on the galaxy listed above and well within its outline, the description fits and there is nothing else nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 2655 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4814 is about 120 to 125 million light-years away, in good agreement with redshift-independent distance estimates of about 90 to 165 million light-years. Given that and its apparent size of about 2.35 by 2.2 arcmin for the main part of the galaxy and about 4.75 by 2.75 arcmin for its faint outer arms (from the images below), the main galaxy is about 85 thousand light-years across, and its outer arms span about 170 thousand light-years.

Historical Identification: Per Dreyer, NGC 4815 (= GC 3317 = JH 3443, 1860 RA 12 49 24, NPD 154 11.8) is "a cluster, pretty large, pretty rich, irregular figure, stars from 10th to 18th magnitude." The second IC adds "According to Innes (7-inch refractor), a nebula involving, but to the south of two stars." The position precesses to RA 12 58 05.7, Dec -64 57 18, about an arcmin northeast of the center of the cluster listed above (though exactly where the center is isn't obvious) and certainly within its boundaries, the description fits and there is nothing else close enough to worry about, so the identification is certain.
Note About PGC Designation: Apparently for purposes of completeness, LEDA assigns PGC designations to almost all NGC/IC objects, regardless of their nature. However, although it correctly lists NGC 4815 as an open cluster, a search of the database for its PGC designation returns no result, hence its being placed in quotes.
Addendum: Gottlieb notes that in 1901 Innes stated that the cluster was not resolvable with his 7-inch refractor (which is correct); but per his 1899 paper, Innes had already observed the cluster in 1898, and was unable to see it as anything but "an irregular nebula surrounding two stars," hence my 1898 date for Innes' observation.
Physical Information: NGC 4815 is thought to be about 10000 light-years away, and contains about 70 more or less certain cluster members. Based on its Hertzsprung-Russell Diagram, it is thought to be about 400 to 500 million years old, and estimates of its diameter, which range from about 5 to 7 arcmin, correspond to about 15 light-years.

Historical Identification: Per Dreyer, NGC 4816 (= GC 3314 = JH 1481 = WH II 383, (d'Arrest), 1860 RA 12 49 25, NPD 61 29.8) is "very faint, pretty large." The position precesses to RA 12 56 12.4, Dec +27 44 40, well within the outline of the galaxy listed above, the description fits and there is nothing comparable nearby, so the identification is certain.
Discovery Note: Gottlieb notes that both Herschels' positions were well to the west of PGC 44114, but does not suggest how Dreyer obtained the correct position for the NGC entry. Knowing that d'Arrest made many observations of GC objects and Dreyer added many of d'Arrest's "novae" and corrections to his 1878 update of the GC, I looked at d'Arrest's paper and found that it contains Dreyer's position for GC 3314; that is why I have added d'Arrest's observation to the discovery list and NGC entry (the latter in parentheses).
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7185 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4816 is about 335 million light-years away, in almost inevitable agreement with redshift-independent distance estimates of about 305 to 540 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 325 million light-years away at the time the light by which we see it was emitted, about 330 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 about 1.5 by 1.2 arcmin (from the images below), the galaxy is about 140 to 145 thousand light-years across.
Possible Companionship: Given their nearly identical recessional velocities and apparent distances, there is a good chance that PGC 44137 is a physical companion of NGC 4816, hence my use of "probable" instead of "possible" companion in its entry.

Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7155 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 44137 is about 330 to 335 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 340 to 375 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 325 million light-years away at the time the light by which we see it was emitted, about 325 to 330 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 about 0.45 by 0.35 arcmin (from the images below), the galaxy is about 40 to 45 thousand light-years across.
Possible Companionship: Given their nearly identical recessional velocities and apparent distances, there is a good chance that PGC 44137 is a physical companion of NGC 4816, hence my use of "probable" instead of "possible" companion in this entry.

Historical Identification: Per Dreyer, NGC 4817 (Bigourdan (list II #60), 1860 RA 12 49 26, NPD 61 15) is "very faint, no nucleus." The second IC adds "Not on Heidelberg plate (W. [Wolf] list III)." The NGC position precesses to RA 12 56 13.2, Dec +27 59 28, but (as stated by Wolf) there is nothing there. The problem is that the position in Bigourdan's list II is incorrect. In Bigourdan's "Big Book" (not published until 1906), as described immediately below, the actual measurements prove that the galaxy listed above is what he saw (and as noted immediately below that, Wolf also saw, but of course had no way of knowing it was NGC 4817), so the identification is certain.
Discussion of Bigourdan's Observations: Bigourdan made two measurements of the position of his #60, which became NGC 4817. His magnitude 10.5 "Anonymous" reference star is listed as having a position of (1900) RA 12 51 17, Dec +28 30, which precesses to (2000) RA 12 56 07.7, Dec +27 57 30. That star, TYC 1995-1852-1, is a magnitude 11.6 star at (2000) RA 12 56 06.9, Dec +27 57 40, or (1900) RA 12 51 16.2, Dec +28 30 10. Adding Bigourdan's offsets from the star to the nebula (+21.63 seconds of time and - 1' 19.6" of declination, Bigourdan #60 should be at (1900) RA 12 51 37.8, Dec +28 28 50, or (2000) RA 12 56 28.5, Dec +27 56 21, which lies only 0.3 arcmin nearly due west of the galaxy listed above. Given that, the fact that the description fits and there is nothing else nearby, the identification of NGC 4817 as PGC 83663 is, as stated above, absolutely certain.
Discussion of Wolf's Observation: Wolf did observe NGC 4817, but since its position in Bigourdan's list II was incorrect, Wolf had no way of knowing that #153 in one of the tables in his list III was NGC 4817 (the table is the same one in which NGC 4798 is shown, but 4797 is not, since its position was also incorrect). Wolf's description reads "extremely small, considerably faint, irregular figure, diffuse, brighter middle."
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6940 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4817 is about 320 to 325 million light-years away, in fair agreement with redshift-independent distance estimates of about 375 to 425 million light-years. Given that and its apparent size of about 0.45 by 0.45 arcmin (from the images below), the galaxy is about 40 to 45 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4818 (= GC 3318 = JH 1484 = JH 3445 = WH II 549, 1860 RA 12 49 33, NPD 97 46.1) is "pretty bright, large, pretty much extended 0°, gradually brighter middle." The position precesses to RA 12 56 49.5, Dec -08 31 37, well within the 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 relative to the Cosmic Microwave Background radiation of 1400 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4818 is about 65 million light-years away, in good agreement with redshift-independent distance estimates of about 35 to 70 million light-years. Given that and its apparent size of about 4.85 by 1.7 arcmin (from the images below), the galaxy is about 90 to 95 thousand light-years across. The galaxy is listed as a starburst galaxy, presumably due to its bright center.
Use By The de Vaucouleurs Atlas: NGC 4818 is used by the de Vaucouleurs Atlas of Galaxies as an example of type I0/SB0 pec. However, other sources list it as type SAB(s)ab or SAB(rs)ab? pec; and "pec" seems appropriate no matter which classification is used.

Historical Identification: Per Dreyer, NGC 4819 (= GC 3324 = JH 1487 = WH II 346, d'Arrest, 1860 RA 12 49 40, NPD 62 15.2) is "very faint, pretty large, irregular figure." The position precesses to RA 12 56 28.1, Dec +26 59 17, well within the outline of the galaxy listed above, the description is a reasonable fit and the only nearby alternative is accounted for by NGC 4821, observed by d'Arrest on the same night, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6735 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4819 is about 310 to 315 million light-years away. Given that and its apparent size of about 1.05 by 0.75 arcmin (from the images below), the galaxy is about 95 thousand light-years across. The central part of the galaxy shows strong emission lines due to gases heated by the large numbers of hot, bright stars lighting up its nucleus and bar. It is possible that NGC 4819 and 4821 are a pair, but the 600 km/sec difference in their recessional velocities either means that the latter galaxy is the best part of 25 to 30 million light-years more distant, or that it is moving (or has moved) past the former at too high a speed for them to be gravitationally bound; the latter possibility (a near passage in the distant past) might explain the peculiarities in their structures.

Historical Identification: Per Dreyer, NGC 4820 (Tempel list V, 1860 RA 12 49 41, NPD 102 58) is "very small, south-preceding of (southwest of) II 563," WH II 563 being NGC 4825. The position precesses to RA 12 57 01.5, Dec -13 43 31, less than 0.5 arcmin south-southeast of the center of the galaxy listed above, the description fits and there is nothing else nearby (save for NGC 4825, which helps confirm the identification), so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4955 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4820 is about 230 million light-years away, in reasonable agreement with a single redshift-independent distance estimate of about 205 million light-years. Given that and its apparent size of about 1.17 by 0.30 arcmin (from the images below), the galaxy is about 75 to 80 thousand light-years across.
Classification Note: The galaxy is obviously a lenticular galaxy of type S0; but the closeup image appears to show a thin dust lane in front of the nucleus, hence the addition of /a? to the type.

Historical Identification: Per Dreyer, NGC 4821 (= GC 5682, d'Arrest, 1860 RA 12 49 42, NPD 62 16.6) is "very faint, very small, II 346 north-preceding (to northwest)," WH II 346 being NGC 4819. The position precesses to RA 12 56 30.1, Dec +26 57 53, less than 0.5 arcmin north-northeast of the galaxy listed above, the description fits and the only nearby alternative is NGC 4819, which is not only noted in the NGC entry, but was observed by d'Arrest on the same night, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7330 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4821 is about 340 million light-years away, in fair agreement with a single redshift-independent distance estimate of about 375 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 330 to 335 million light-years away at the time the light by which we see it was emitted, about 335 to 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 about 0.53 by 0.35 arcmin (from the images below), the galaxy is about 50 to 55 thousand light-years across. It is possible that NGC 4819 and 4821 are a pair, but the 600 km/sec difference in their recessional velocities either means that the latter galaxy is the best part of 25 to 30 million light-years more distant, or that it is moving (or has moved) past the former at too high a speed for them to be gravitationally bound; the latter possibility (a near passage in the distant past) might explain the peculiarities in their structures.

Historical Identification: Per Dreyer, NGC 4822 (Tempel list V (#22), 1860 RA 12 49 46, NPD 100 00.0) is "faint, star involved." The position precesses to RA 12 57 04.2, Dec -10 45 30, on the northeastern rim of the galaxy listed above, the only problem with the description is that there is no star "involved" (probably the bright nucleus was mistaken for a star), and there is nothing else anywhere nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4260 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4822 is about 195 to 200 million light-years away, in fair agreement with a single redshift-independent distance estimate of about 170 million light-years. Given that and its apparent size of about 1.5 by 1.05 arcmin (from the images below) plus some faint dusty regions that erratically extend in various directions spanning a region about 1.75 by 1.25 arcmin in size (hence my classifying it as a peculiar galaxy), the central galaxy is about 85 thousand light-years across, and its outer regions are about 100 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4823 (Tempel list V, 1860 RA 12 49 47, NPD 102 55) is "very small, south-preceding of (southwest of) II 563," WH II 563 being NGC 4825. The position precesses to RA 12 57 07.5, Dec -13 40 30, but there is nothing there. However, Corwin notes that Tempel observed three nebulae near NGC 4825 (NGC 4820, 4823 and 4829) all of which are described as "very small", and none of which have positions in Tempel's list V (per p. 11 of the NGC, he must have sent positions to Dreyer by private communication). The position for 4823 is obviously wrong, but the other two galaxies have good positions, and since there are only three small galaxies near NGC 4825, 4823 must be the one that isn't 4820 or 4829, which means it must be the one shown for this entry. That isn't as satisfactory an identification as one might like, but the positional error is almost exactly 20 seconds of time in right ascension and 1 arcmin in declination, which suggests some kind of blunder in addition or subtraction by Tempel, and in any event, either NGC 4823 is the galaxy listed above, or Tempel didn't actually see three nebulae, and the former possibility seems far more likely than the latter, so the identification is essentially certain.
Misidentification As NGC 4829: Per Gottlieb, the RNGC and the original PGC reversed the identifications for NGC 4823 and 4829; but HyperLEDA has corrected the error in the PGC designation, so the correct identification is shown on that site. However, other sites (e.g., SIMBAD) still misidentify this galaxy as NGC 4829, hence the warning in the title for this entry.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4935 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4823 is about 230 million light-years away. Given that and its apparent size of about 0.9 by 0.25 arcmin (from the images below), the galaxy is about 60 thousand light-years across.
Classification Note: It may merely be an artifact, but the closeup image appears to show an X-shaped double bar centered on the nucleus, which is a feature seen in some other lenticular galaxies. The S0/a classification is based on the LEDA and NED databases; but the "pec?" was added in case the X-shaped feature is real. (Note: The brightish spot near the southern end of the galaxy is a foreground star, and therefore has nothing to do with the galaxy or its structure.)

Historical Identification: Per Dreyer, NGC 4824 (Bigourdan (list II #61), 1860 RA 12 49 48, NPD 61 48.0) is "very faint, very small." The position precesses to RA 12 56 35.6, Dec +27 26 29, only half an arcmin north-northwest of the star listed above, the description is typical of the many stars Bigourdan mistakenly listed as very faint, very small nebulae, and there is nothing else nearby, so the identification is certain. However, LEDA (and many other catalogs) misidentifies NGC 4824 as PGC 44162, a galaxy about 6.4 arcmin north of NGC 4824 (and therefore out of the field of view in the image shown here), and although NED lists NGC 4824 as the star above and has a warning about the misidentification with PGC 44162, it also lists a redshift-independent distance estimate of about 350 to 355 million light-years for the star, which undoubtedly belongs to PGC 44162, and proves that a warning is necessary! For that reason, PGC 44162 is discussed in the following entry, specifically as a warning about the misidentification.

Historical Misidentification: As noted in the entry for NGC 4824, that is only a magnitude 15.2 star; however, it is not unusual in such cases for modern catalogers to choose the nearest "suitable" galaxy as the NGC object, and in this case, PGC 44162, which lies about 6 1/2 arcmin due north of the star that really is NGC 4824 (and is therefore completely out of frame in the image for that object), was chosen instead of the correct identification. As noted in the entry for NGC 4824, even in cases where the identity as a star is correctly shown, data applying to the galaxy can show up, hence the need to have a clear warning, such as this entry, about the misidentification.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7375 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 44162 is about 340 to 345 million light-years away, in reasonable agreement with redshift-independent distance estimates of 350 to 375 million light-years (one from the NED entry for the star, and one from its entry for the galaxy, but both obviously really for the galaxy). 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 330 to 335 million light-years away at the time the light by which we see it was emitted, about 335 to 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 between about 0.36 by 0.32 arcmin and 0.39 by 0.36 arcmin (from the images below), the galaxy is about 35 to 40 thousand light-years across.
Discussion Of The Two Close-Up Images: At first glance PGC 44162 appears to be a more or less ordinary elliptical galaxy about 0.36 by 0.32 arcmin in size (and therefore, type E1, as listed in LEDA); but high-contrast images increase that to about 0.39 by 0.36 arcmin (also type E1). The high-contrast image also shows what appears to be a partial ring to the north of the galaxy but that is probably simply an illusion created by an arc of foreground stars, so barring a surprise when better-quality images become available, the galaxy is almost certainly type E1.

Historical Identification: Per Dreyer, NGC 4825 (= GC 3320 = WH II 563, 1860 RA 12 49 51, NPD 102 54.6) is "pretty bright, irregular figure, brighter middle." The position precesses to RA 12 57 11.5, Dec -13 40 06, on the southwestern rim of the galaxy listed above, the description is a reasonable fit and there is nothing comparable nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4785 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4825 is about 220 to 225 million light-years away, in good agreement with redshift-independent distance estimates of about 110 to 230 million light-years. Given that and its apparent size of about 2.2 by 1.35 arcmin (from the images below), the galaxy is about ? thousand light-years across.
Note About Possible Companion: Corwin lists 2MASS J12571108-1339100 (at RA 12 57 11.1, Dec -13 39 10) as a possible companion, but no information is available for that object, so nothing can be said about it, except that it has an apparent size of about 0.22 by 0.19 arcmin (from the images below), making it (most likely) a type E1 elliptical galaxy..

Historical Identification: Per Dreyer, NGC 4826 (= GC 3321 = JH 1486, M64, 1860 RA 12 49 51, NPD 67 33.5) is a "remarkable object, very bright, very large, very much extended 120°±, brighter middle suddenly bright nucleus". The position precesses to RA 12 56 43.8, Dec +21 40 59, dead center on the galaxy listed above and the description fits, so the identification is certain.
Note About The Nickname: Though William Herschel did not publish his observation (since the object was already well-known as M64), his sweep 699 entry notes the "small black arch" within the object; and when John Herschel published his own sketch of the object he wrote "...seen by my Father, and shown by him to the late Sir Charles Blagden, who likened it to the appearance of a black eye, an odd, but not inapt comparison." So the nickname "Black Eye" is over two centuries old, though the fact that it was a galaxy had to wait until the existence of other galaxies was finally proven by Hubble in the early 1920's.
Discovery Notes: Bode's observation was published in 1779 and Messier's in 1780, but Pigott's observation was not published until read at the Royal Society in London on Jan 11, 1781; as a result of its late report it was essentially ignored for more than 200 years and only brought to modern notice by Bryn Jones in April 2002.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 700 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4826 is about 30 to 35 million light-years away, in poor agreement with redshift-independent distance estimates of about 8 to 24 million light-years and the HST press release estimate of 17 million light-years. The reason for the difference is probably a "peculiar velocity" (that is, a motion relative to its neighbors that has nothing to do with the Universal Expansion) of about 350 km/sec away from us and our neighbors; this is a little larger than typical peculiar velocities of nearby galaxies, but not much larger, and is a reason that for such close objects distances based on their recessional velocities are often at odds with redshift-independent distances. Using the 17 million light-year distance and its apparent size of about 10.0 by 4.75 arcmin (from the images below), the galaxy is about 50 thousand light-years across. Although the stars and gas in its central structure are moving in the direction expected from its spiral appearance (clockwise, in the views shown below), the gas in its outer regions is moving in the opposite direction. This is probably the result of a collision and subsequent merger with a smaller galaxy, a billion or so years ago; but whatever the reason, collisions of clouds of gas and dust within the boundary between the two regions have led to a chaotic burst of star formation, giving the core of the galaxy an unusually dramatic appearance, and causing it to be classified as a Seyfert galaxy (type Sy2).
Use By The de Vaucouleurs Atlas: NGC 4826 is used by the de Vaucouleurs Atlas of Galaxies as an example of type (R')SA(r)ab pec.

Historical Identification: Per Dreyer, NGC 4827 (= GC 3319 = JH 1485 = WH II 384, 1860 RA 12 49 53, NPD 62 03.8) is "faint, considerably large." The position precesses to RA 12 56 40.8, Dec +27 10 41, about 0.6 arcmin nearly due west of the center of the galaxy listed above, the description is reasonable and there is nothing else nearby, so the identification is certain.
Discovery Note: Although not mentioned by Dreyer, so I would not normally mention it either, Gottlieb notes that d'Arrest observed the galaxy on four occasions, hence the addition of his name to the list of observers.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7905 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4827 is about 365 to 370 million light-years away, in good agreement with redshift-independent distance estimates of about 345 to 415 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 355 to 360 million light-years away at the time the light by which we see it was emitted, about 360 to 365 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 about 1.4 by 1.2 arcmin (from the images below), the galaxy is about 145 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4828 (= GC 5683, d'Arrest, 1860 RA 12 49 53, NPD 61 13.3) is "faint, small, round." The position precesses to RA 12 56 40.0, Dec +28 01 11, about 0.6 arcmin nearly due west of the center 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 relative to the Cosmic Microwave Background radiation of 6565 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4828 is about 305 million light-years away, in fair agreement with a single redshift-independent distance estimate of about 375 million light-years. Given that and its apparent size of about 0.75 by 0.65 arcmin (from the images below), the galaxy is about 65 to 70 thousand light-years across. The galaxy has an unusually bright nucleus, more or less surrounded by a dusty nuclear ring, and perhaps deserves to have "pec" added to its type.

Historical Identification: Per Dreyer, NGC 4829 (Tempel list V, 1860 RA 12 50 03, NPD 102 59) is "very small, south-following (southeast of) II 563," WH II 563 being NGC 4825. The position (not listed in Tempel's list V and presumably privately communicated to Dreyer) precesses to RA 12 57 23.6, Dec -13 44 30, less than 0.4 arcmin southwest of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain. However, several catalogs reverse the identifications of NGC 4823 (which see) and 4829, thanks to the incorrect NGC position for 4823 causing a considerable amount of confusion, hence the warning about the possible misidentification in the title of this entry.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4220 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4829 is about 195 to 200 million light-years away, in fair agreement with a single redshift-independent distance estimate of about 265 million light-years. Given that and its apparent size of about 0.5 by 0.3 arcmin (from the images below), the galaxy is about 25 to 30 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4830 (Temple lists IV (#9) and V (#23), 1860 RA 12 50 03, NPD 108 56.0) is "faint, large, star involved, 8th magnitude star 5 arcmin south-following (to southeast)." The position precesses to RA 12 57 28.5, Dec -19 41 30, well within the eastern outline of the galaxy listed above, the description is a perfect fit and there is nothing comparable nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 3680 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4830 is about 170 to 175 million light-years away, in good agreement with redshift-independent distance estimates of about 105 to 195 million light-years. Given that and its apparent size of about 1.9 by 1.2 arcmin, though fainter outer regions appear to span about 2.5 by 1.35 arcmin (from the images below), the main galaxy is about 95 thousand light-years across, and if the fainter outer regions aren't just a photographic illusion, they span about 125 thousand light-years. Since its apparent companion (PGC 44312) has a recessional velocity only about 300 km/sec larger, they might be physical companions, but it's just as likely that the smaller galaxy is 15 million light-years beyond its apparent neighbor, and they aren't physical companions at all.

Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4000 km/sec (and H₀ = 70 km/sec/Mpc), PGC 44312 is about 185 to 190 million light-years away. Given that and its apparent size of about 0.4 by 0.3 arcmin (from the images in the preceding entry), the galaxy is about 20 to 25 thousand light-years across. As noted in the entry for NGC 4830, the two galaxies might be actual companions, but their recessional velocities are sufficiently different that it's just as likely that the smaller galaxy is about 15 million light-year further away, and they aren't physcial companions at all.

Historical Identification: Per Dreyer, NGC 4831 (= GC 3322 = JH 3447, (W. Herschel), 1860 RA 12 50 06, NPD 116 32.2) is "faint, small, round, gradually brighter middle". The position precesses to RA 12 57 38.4, Dec -27 17 41, only 0.4 arcmin east-southeast of the center of the galaxy listed above and barely outside its eastern outline, the description fits and there is nothing else nearby, so the identification is certain.
Discovery Notes: William Herschel observed this object with his 40-foot telescope, but never published the observation, so it does not appear in the GC or NGC. Wolfgang Steinicke found the observation while analyzing the elder Herschel's 40-foot sweep data (hence its being in parentheses in the NGC entry shown here).
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 3635 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4831 is about 170 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 105 to 160 million light-years. Given that and its apparent size of about 1.7 by 1.0 arcmin (from the images below), the galaxy is about 80 to 85 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4832 (= GC 3323 = JH 3446, 1860 RA 12 50 06, NPD 129 59.6) is "pretty faint, very small, round, suddenly brighter middle equal to 17th magnitude star, 10th magnitude star at position angle 70°.3." The position precesses to RA 12 57 53.4, Dec -40 45 05, but there is nothing there. However, it turns out that Herschel made a 1 degree typo in the NPD when reducing his observations at the Cape of Good Hope for the publication of his GC, as the entry for JH 3446 in his catalog of observations in South Africa corresponds to an 1860 NPD of 128 59.6. Correcting for that error, the position precesses to RA 12 57 52.1, Dec -39 45 05, which is about 1 arcmin northeast of the galaxy listed above, which exactly fits the description; so there is absolutely no doubt that PGC 44361 is what Herschel observed.
Addendum: Gottlieb also caught the 1 degree error in the NPD, and also ascribed it to the typo by JH that was simply copied by Dreyer from the GC, as Dreyer had no reason to suspect that it was incorrectly transferred from the Cape of Good Hope entry. And per a private communication by Corwin, he and Antoinette de Vaucouleurs noticed the error in 1976.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4030 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4832 is about 185 to 190 million light-years away, in fair agreement with redshift-independent distance estimates of about 120 to 155 million light-years. Given that and its apparent size of about 2.0 by 1.5 arcmin for the central galaxy and its faint outer (ring?) (from the images below), the galaxy is about 110 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4833 (= GC 3325 = JH 3444, Lacaille list I #4, Dunlop #164, 1860 RA 12 50 08, NPD 160 06.9) is "a globular cluster, bright, large, round, gradually, then very suddenly brighter middle, stars of 12th magnitude". The position precesses to RA 12 59 23.2, Dec -70 52 21, well within the western outline of the cluster listed above, the cluster is obviously the object described and there is nothing else nearby, so the identification is certain.
Note About PGC Designation: For purposes of completeness, LEDA assigns a PGC designation to almost all NGC/IC objects, regardless of their nature. However, although the LEDA page for NGC 4833 correctly shows that it is a globular cluster, a search of the database for its PGC designation returns no result, hence its being placed in quotes.
Physical Information: NGC 4833 is about 22 thousand light-years away (give or take a few hundred light-years), and has an apparent size (depending on different visual "isophotes") of about 13.5 to 15.5 arcmin. Based on that, it is about 85 to 95 light-years in diameter. Age estimates based on its Hertzsprung-Russell Diagram range from about 11.7 to 12.5 billion years, meaning that it may be one of the oldest globular clusters in our galaxy.

Historical Identification: Per Dreyer, NGC 4834 (= GC 3326 = JH 1488 = WH III 817, 1860 RA 12 50 11, NPD 36 56.7) is "very faint, small, irregularly round, brighter middle." The position precesses to RA 12 56 24.7, Dec +52 17 48, within the southwestern 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 relative to the Cosmic Background Radiation of 11415 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4834 is about 530 to 535 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 505 to 510 million light-years away at the time the light by which we see it was emitted, about 515 to 520 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 about 0.95 by 0.4 arcmin (from the images below), the galaxy is about 140 thousand light-years across.
Classification Note: Presumably based on the brightness of the nucleus, strong emission by gases excited by hot, bright young stars and the poorly delineated spiral structure, all the references I can find list this as some type of Sa galaxy, but the quality of the images below is too poor for me to agree to any of the more detailed classifications, so just a plain Sa with a very big question mark seems the only justifiable "type" until better images are available.

Historical Identification: Per Dreyer, NGC 4835 (= GC 3327 = JH 3448, 1860 RA 12 50 15, NPD 135 30.0) is "faint, pretty large, much extended, very gradually brighter middle." The position precesses to RA 12 58 10.5, Dec -46 15 28, just over 0.5 arcmin northeast of the galaxy listed above, the description is a perfect fit and there is nothing comparable nearby, so the identification is certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 2440 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4835 is about 110 to 115 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 55 to 105 million light-years. Given that and its apparent size of about 4.4 by 1.25 arcmin (from the images below), the galaxy is about 145 thousand light-years across. The faint galaxy to its southwest, PGC 516792, is probably a physical companion, and is therefore discussed in the following entry.

Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 2490 km/sec (and H₀ = 70 km/sec/Mpc), PGC 516972 is about 115 million light-years away, more or less the same as its presumed companion, NGC 4835. Given that and its apparent size of about 1.1 by 0.35 arcmin (from the images below), the galaxy is about 35 to 40 thousand light-years across.
Classification Note: Most references list no "type" for this galaxy, and although LEDA lists it as type Sd, the lack of any obvious structure in the images here and above seems to better justify classifying it as an irregular galaxy, as I have done above. Still, that's how the Magellanic Clouds were once listed, and they are now considered late-type spirals seen at an unfortunate angle, so perhaps better images will change the classification(s) shown here.

Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 3645 km/sec (and H₀ = 70 km/sec/Mpc), PGC 44271 is about 170 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 140 to 160 million light-years. Given that and its apparent size of about 2.9 by 0.25 arcmin (from the images below), the galaxy is about 140 to 145 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4836 (Tempel list V (#24), 1860 RA 12 50 15, NPD 101 59.2) is "very faint, large, diffuse." The position precesses to RA 12 57 34.9, Dec -12 44 41, well within the eastern 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 relative to the Cosmic Microwave Background radiation of 5480 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4836 is about 255 million light-years away. Given that and its apparent size of about 1.4 by 1.1 arcmin (from the images below), the galaxy is about 105 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4837 (= GC 3328 = JH 1489, 1860 RA 12 50 23, NPD 40 26.2) is "nebulous; ?" The position precesses to RA 12 56 43.1, Dec +48 48 18 (whence the first position given above), but there is nothing there; and that, the fact that Herschel only observed the "object" once and the question mark in his description led Malcolm Thomas to decide that the object is nonexistent. However, it is possible that Herschel made a single-digit 30 arcmin typo in the GC and the NPD should be 40 56.2, in which case the position would precess to RA 12 56 44.0, Dec +48 18 18, which is only 0.9 arcmin northwest of the pair of interacting galaxies listed above, so CGCG listed that as NGC 4837, and Corwin admits that is a reasonable possibility. As many or more catalogs agree with that as agree with Thomson, so if NGC 4837 is listed as an actual object, that pair is the one listed. Obviously the identification cannot be considered certain, but it isn't unreasonable, especially since Gottlieb notes that Herschel listed the same object with a 30 arcmin difference in the NPD on another night (in the wrong direction, making the error in the position a full degree); so it seems quite likely that the NPD was wrong, and this pair is the correct "object".
Note About The PGC Designations: Although the original PGC gave designations to the individual galaxies, their identification as NGC 4837 had not been established; and by the time it was, though HyperLEDA assigned a new PGC designation for the NGC entry, a search of the database for that designation returns no result, so it has been placed in quotes.
Physical Information: As an interacting pair, the appropriate recessional velocity of NGC 4837 is the average of the individually measured galaxies' recessional velocities (8770 km/sec for PGC 44188 and 8760 km/sec for PGC 44198). Based on the average recessional velocity relative to the Cosmic Background Radiation of 8765 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4837 is about 405 to 410 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 pair was about 395 million light-years away at the time the light by which we see it was emitted, about 400 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 about 0.7 by 0.3 arcmin for PGC 44188 and about 0.75 by 0.3 arcmin for PGC 44189 (from the images below), PGC 44188 is about 80 thousand light-years across, PGC 44198 is about 85 thousand light-years across, and the about 12.5 by 0.5 arcmin wide apparent size of the pair (also from the images below) corresponds to about 140 to 145 thousand light-years.

Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 9220 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 214043 is about 430 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 415 million light-years away at the time the light by which we see it was emitted, about 420 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 about 0.5 by 0.35 arcmin (from the images below), the galaxy is about 60 thousand light-years across. Given its appaently larger distance, PGC 214043 is probably not a physically bound companion of NGC 4837, but may have passed by it at some point in the distant past, and is at least in the same "general" region of space.
Whether the faint galaxy just to the northeast of PGC 214043 is in any way related to it is unknown, as there appears to be no information available for it, save its position and (very) small apparent sie.

Historical Identification: Per Dreyer, NGC 4838 (= GC 3329 = JH 1490, Tempel list V, 1860 RA 12 50 36, NPD 102 18.0) is "very faint, pretty small, round, 3 small (faint) stars south-preceding (to southwest)." The position (per p.11 of the NGC, undoubtedly privately sent to Dreyer) precesses to RA 12 57 56.2, Dec -13 03 28, barely north 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 relative to the Cosmic Microwave Background radiation of 5350 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4838 is about 250 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 160 to 235 million light-years. Given that and its apparent size of about 2.2 by 1.8 arcmin for the central galaxy and about 3.35 by 2.95 for a finat partial outer ring (on its northrn side) (from the images below), the main galaxy is about 160 thousand light-years across, and with the partial ring spans 240 to 245 thouand light-years.

Historical Identification: Per Dreyer, NGC 4839 (= GC 3333 = JH 1494 = WH II 386, d'Arrest, 1860 RA 12 50 36, NPD 61 44.9) is "faint, pretty large, round." The position precesses to RA 12 57 23.2, Dec +27 29 37, within the southwestern outline of the galaxy listed above, the description fits and there is nothing comparable nearby, so the identification is certain.
Discovery Note: Per Gottlieb, William Herschel's position was 3 arcmin south of the galaxy listed above, and his son John apparently used that position for the GC (namely 1860 RA 12 50 55.4, NPD 61 49 52.2), but d'Arrest measured a position 5 arcmin to the north of the one in the GC, and that's the position Dreyer used for the NGC.
Warning About Misidentification: NED notes that at least one source misidentifies NGC 4839 as PGC 83677, hence its entry below, serving as a warning about that error.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7635 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4839 is about 355 million light-years away, in almost inevitable agreement with redshift-independent distance estimates of about 90 to 485 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 345 million light-years away at the time the light by which we see it was emitted, about 350 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 the apparent size of about 4.0 by 1.8 arcmin of its extended outer regions (from NED and the images below), the galaxy is about 400 thousand light-years across, making it a truly immense (and massive) object. Although not visible in the images shown here, the galaxy is known to have a strong radio jet, presumably from a supermassive black hole at its center. As noted in the following entry, NGC 4839's apparent companion, PGC 83685, must actually be a background galaxy seen through the foreground galaxy.

Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 8515 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 83685 is about 395 to 400 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 380 to 385 million light-years away at the time the light by which we see it was emitted, about 390 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 about 0.2 by 0.1 arcmin (from the image below), the galaxy is about 20 to 25 thousand light-years across. Although listed as an apparent companion of NGC 4839, the nearly 1000 km/sec difference in their recessional velocities and nearly 40 million light-year difference in their corresponding distances almost certainly means that PGC 83685 is merely a background galaxy seen through its apparent "companion". They may well be part of the same cluster of galaxies, but are almost certainly not physical companions.

Historical Misidentification: There should be no question about the identity of NGC 4839, but it is not uncommon for galaxies to be misidentified in one place or another, and as noted in the entry for NGC 4839, it has been misidentified as PGC 83677, hence my placing this entry here as a warning.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6485 km/sec (and H₀ = 70 km/sec/Mpc), PGC 83677 is about 300 to 305 million light-years away, in good agreement with a Hubble Space Telescope website distance estimate (presumably based on its cluster membership) of about 300 million light-years. The apparent size of its outer ring is about 0.75 by 0.7 arcmin, while the brighter central region spans about 0.35 by 0.3 arcmin (all sizes from the images below). Given that and its distance, the outer ring spans about 65 thousand light-years, and the brighter central region about 30 thousand light-years. The galaxy's core is so bright (it is classified as a type S1 Seyfert galaxy) because it is the site of a "monstrous" black hole that is spewing out huge amounts of ultraviolet and X-radiation, as well as the visible light shown in the images below. The close-up HST images suggest that there is a bluish ring surrounding the central core, so the structure may be even more complicated than indicated by the "type" shown in the description line.

Historical Identification: Per Dreyer, NGC 4840 (= GC 5684 = WH II 385, d'Arrest, 1860 RA 12 50 45, NPD 61 38.6) is "very faint, very small." The second IC lists a corrected NPD (per W. [Wolf] III) of 61 29.5. The original NGC position precesses to RA 12 57 32.0, Dec +27 35 56, only about 0.7 arcmin south-southwest of the galaxy listed above, the description fits and there is nothing else nearby, so the identification seems certain. (So what about Wolf's "correction"? See the following paragraphs for a discussion of that.)
Wolf's "Observation" Of NGC 4840: Wolf's supposed correction for NGC 4840 precesses to RA 12 57 31.9, Dec +27 45 02, but there is nothing there but a magnitude 13 star. Obviously, Wolf made some kind of mistake, which must be in his list III, which contains all his observations (over 1500!) of nebulae near the North Galactic Pole. On page 142 of his paper Wolf lists NGC 4840 with a question mark, at (1875) RA 12 51 31.5, NPD 61 34 19, as "extremely small, pretty faint." That position precesses to (1860) RA 12 50 47.8, NPD 61 29.4, which is essentially the "corrected" position provided by Dreyer in the IC2. So either Wolf mistook the star for a nebula, or there was a plate flaw near the position of what he thought might be NGC 4840 (I say might, since his question mark shows that he wasn't at all sure that it was). but whatever he thought he saw at that position, it cannot have been any nebula, let alone NGC 4840.
Did Wolf See NGC 4840 At All?: Although Wolf's "observation" of NGC 4840(?) must have involved some kind of error, he did record thousands of objects on the plate of the region, so it is possible that one of his "novae" was the same as d'Arrest's "nova", and therefore NGC 4840. As an example, PGC 83686, which lies just west of Wolf's position for "4840", has a position of (2000) RA 12 57 23.3, Dec +27 40 01, which precesses to (1875) RA 12 51 20.1, Dec +28 26 36 (= NPD 61 33 24). Looking at Wolf's list III, we find that #168 on page 142 is at RA 12 51 20.2, NPD 61 33 27, which is essentially the same, so Wolf certainly observed PGC 83686. Similarly, PGC 83695, at (2000) RA 12 57 46.1, Dec +27 45 27 = (1875) RA 12 51 43.0, Dec +28 26 01 (= NPD 61 33 59), must be #185 on the same page, at RA 12 51 43.0, NPD 61 34 04. In other words, if there was something near what Wolf thought was NGC 4840, he accurately recorded it (meaning that as stated above, his "4840 (?)" must have been the star or plate flaw suggested in the previous paragraph). Given that, what about objects that he recorded in the region near the actual NGC 4840?
 To resolve that question, we precess the modern position (2000) RA 12 57 32.8, Dec +27 36 37 to the equinox of Wolf's list: (1875) RA 12 51 29.5, Dec +28 17 12 (= NPD 61 42 48), and examine his tables, but without any success; there is nothing within 4 arcmin of NGC 4840's NPD anywhere near its right ascension. In response to a query about this, Corwin has informed me that he has a contact print of Wolf's plate, and that on that print NGC 4840 looks just like a 15th magnitude star, and is not marked with a 'v', which is how Wolf filled the plate with his nebular observations; so Wolf did not observe NGC 4840, after all.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6360 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4840 is about 295 to 300 million light-years away, in poor agreement with redshift-independent distance estimates of about 345 to 375 million light-years, but good agreement with the roughly 300 million light-year distance of the Coma Cluster. Given that and its apparent size of about .7 by .5 arcmin (from NED and the images below), the galaxy is about 60 thousand light-years across.
Classification Note: The classification as S0/a? is based on the reddish streak below the nucleus; but that may be an image artifact, in which case the classification should simply be (S0?).

Historical Identification: Per Dreyer, NGC 4841 (= GC 3331 = JH 1493 = WH II 387, 1860 RA 12 50 46, NPD 60 46.0) is "pretty faint, pretty large, round, very small (faint) star attached." The position precesses to RA 12 57 32.2, Dec +28 28 32, almost dead center on the galaxy listed above, but the "star attached" is an apparent companion, (PGC 44329), so the identification is certain, except for one thing:
 Should only the galaxy above be thought of as NGC 4841, and its apparent companion as something seen but not part of it? Or should both galaxies be considered part of NGC 4841, since they were seen, even though their nature was misrepresented in the NGC? The standard historical answer is based on John Herschel's writing, who described his observation (per Gottlieb) as "pretty faint, double, north-following, distance 20 arcsec," which is a reasonably accurate description of the pair of galaxies, but who changed that description in his General Catalog to the one copied by Dreyer for the NGC. If Herschel had said "double" in the GC, both galaxies would be part of NGC 4841; but since he didn't do that, the standard definition of NGC 4841 became just the galaxy listed above, and its companion was assigned the bastardized designation of "NGC 4841B" by de Vaucouleurs, and is discussed in the entry immediately following this one, instead of as part of NGC 4841.
Designation Note: CGCG treats PGC 44323 and PGC 44329 as part of the same object, hence the use of N and S to distinguish them.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7045 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4841 is about 325 to 330 million light-years away, in good agreement with redshift-independent distance estimates of about 210 to 340 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 nearly 320 million light-years away at the time the light by which we see it was emitted, nearly 325 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 about 1.3 by 1.0 arcmin (from NED and the images below), the galaxy is about 120 thousand light-years across.

Historical Discussion And Warning About Non-Standard Designations: As noted in the entry for NGC 4841, there is historical uncertainty about whether PGC 44329 should be considered to be part of NGC 4841 or merely an apparent companion, with the standard answer being "only a companion." As it happens, it may not even be a companion, but only an optical double, since (as shown by comparing the two entries) its recessional velocity is nearly 500 km/sec less than that of NGC 4841, meaning that is almost certainly a foreground object. Either way the galaxy is often called "NGC 4841B", but as stated in many places in this catalog, the use of such non-standard designations has led to many cases in which data belonging to one galaxy are mistakenly assigned to a different one, and as a result, such non-standard designations should never be used. (As an example, HyperLEDA shows NGC 4841 and PGC 44329 as having the same brightness, which is obviously wrong, and almost certainly a result of the magnitude of the brighter component being mistakenly assigned to the fainter one.) No matter what people think about whether PGC 44329 should be part of NGC 4841 or not, they should use one of its other designations, not the non-standard NGC designation.
Designation Note: CGCG treats PGC 44323 and PGC 44329 as part of the same object, hence the use of N and S to distinguish them.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6570 km/sec (and H₀ = 70 km/sec/Mpc), PGC 44329 is about 305 million light-years away, in almost inevitable agreement with redshift-independent distance estimates of about 275 to 485 million light-years. Given that and its apparent size of about .65 by .55 arcmin (from the images below), the galaxy is about 55 to 60 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4842 (= GC 5685, d'Arrest, 1860 RA 12 50 46, NPD 61 44.2) is "very faint, very small, h 1494 south-preceding (to southwest)," JH 1494 being NGC 4839. The position precesses to RA 12 57 33.1, Dec +27 30 20, about 0.9 arcmin northwest of the galaxy listed above, the description fits and there is nothing comparable nearby, so the identification is certain.
 It's interesting to note that d'Arrest's original description states that this nebula is 12 seconds of time to the east of h 1494, and concludes by stating that (as a result) the actual position is probably 2 or 3 seconds of time larger than the position he gave for it, which would put it at exactly the same right ascension as the galaxy actually has, making the identification even more certain. So that leaves only one question, similar to the one for NGC 4841: Is NGC 4842 only the galaxy in question, or does its apparent companion (in this case PGC 44338) also belong to the NGC "object"? The similarity to NGC 4841 is that as in that case, some references say yes, and others say no. I would argue that since there is nothing in d'Arrest's detailed description that suggests he saw the fainter "companion", and in fact it might well be too faint for him to have seen at all, it should be considered to be a companion, and not part of NGC 4842. As a result, PGC 44338's properties are not discussed in this entry, but in the one immediately below.
Designation Note: CGCG treats PGC 44337 and PGC 44338 as part of the same object, hence the use of N and S to distinguish them.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7615 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4842 is about 355 million light-years away, in reasonable agreement with a single redshift-independent distance estimate of about 375 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 345 million light-years away at the time the light by which we see it was emitted, about 350 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 about 0.7 by 0.6 arcmin (from the images below), the galaxy is about 70 thousand light-years across. Note that although its southern companion is not part of NGC 4842, their similar distances suggest that they may actually be physical companions.

Historical Misidentification: As noted in the entry for NGC 4842, one might ask whether PGC 44338 should be considered to be part of NGC 4842, and some references treat it exactly that way. But as argued there, odds are that d'Arrest did not and probably could not notice the fainter companion, so it is treated here as only a companion of NGC 4842.
Warning About Non-Standard Designation: As stated in many places in this catalog, using non-standard letter designations for non-NGC/IC objects almost inevitably leads to confusion and mistakes that could be otherwise avoided, so such non-standard designations should never be used, and "NGC 4842B" is only shown here as a warning about such usage.
Designation Note: CGCG treats PGC 44337 and PGC 44338 as part of the same object, hence the use of N and S to distinguish them.
Physical Information: Based on a recessional velocity relative to the Cosmic Background Radiation of 7505 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that PGC 44338 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 about 0.4 by 0.2 arcmin (from the images below), the galaxy is about 40 thousand light-years across. Note that although PGC 44338 is not part of NGC 4842, the two galaxies' similar distances suggest that they may actually be physical companions.

Historical Identification: Per Dreyer, NGC 4843 (= GC 3332 = JH 1492 = WH III 613, 1860 RA 12 50 48, NPD 92 51.4) is "considerably faint, extended, extremely mottled but not resolved, star south-following 30 arcsec (to southeast)." The position precesses to RA 12 58 00.8, Dec -03 36 52, only 0.4 arcmin due north 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 relative to the Cosmic Microwave Background radiation of 5250 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4843 is about 245 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 205 to 235 million light-years. Given that and its apparent size of about 2.6 by 0.55 arcmin (from the images below), the galaxy is about 185 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4844 (Tempel list V (#25b), 1860 RA 12 50 51, NPD 102 18.6) is "faint, small." No position is mentioned in Tempel's paper, but per p.11 of the NGC, he must have sent the NGC position to Dreyer by private communication. That position precesses to RA 12 58 11.2, Dec -13 04 03, but there is nothing there but a few faint stars. Given Tempel's description and the size of his instrument, odds are that what he observed was the brightest of those stars, namely the one listed above, which lies about 1.1 arcmin to the southwest of the NGC position; for if he had mistaken one of the considerably fainter stars (or some combination of them) for a nebula he would almost certainly have written "extremely faint."
Alternate Identification Disclaimer: Gottlieb assigns NGC 4844 to the magnitude 15.5(?) star superimposed on the eastern side of NGC 4838, but Steinicke rejects that possibility, and although Corwin gives a tentative nod to Gottlieb's suggestion, his preferred identification is the star listed above. In any event, if Temple's #25b was the star superimposed on NGC 4838, why would he have sent Dreyer a position so far from the galaxy? Given that question, I also cannot help but reject that possibility.
Note About PGC Designation: For purposes of completeness, LEDA assigns a PGC designation to almost all NGC/IC objects, regardless of their nature; however, a search of the database for that designation returns no result, so it is shown in quotes.

Historical Identification: Per Dreyer, NGC 4845 (= GC 3330 = JH 1491 = WH II 536, 1860 RA 12 50 52, NPD 87 40.4) is "pretty faint, pretty large, pretty much extended, very gradually brighter middle, star north-following (to northeast at position angle) 30°." The position precesses to RA 12 58 00.8, Dec +01 34 08, barely south of the outline of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain. (See NGC 4910 for a discussion of the possible double listing.)
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1560 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4845 is about 70 to 75 million light-years away, in good agreement with redshift-independent distance estimates of about 50 to 100 million light-years (the HST press release uses "over 65 million light-years", which is reasonable given the galaxy's probable membership in the Virgo Cluster, but can't be considered any more accurate). Given that and its apparent size of about 5.6 by 1.2 arcmin (from the images below), the galaxy is about 115 to 120 thousand light-years across. The galaxy is listed as a Seyfert galaxy (type Sy 2), and has unusually strong emission lines caused by interstellar gases heated by large numbers of bright stars or star clusters.

Historical Identification: Per Dreyer, NGC 4846 (= GC 3334 = JH 1495, 1860 RA 12 51 09, NPD 51 52.1) is "extremely faint." The second IC notes "NPD 52 52 (not 51°), per Wolf list V (#95). h. had only one observation." The original NGC position precesses to RA 12 57 45.2, Dec +37 22 27, but there is absolutely nothing there, nor anywhere near there. However, the one degree error (presumably a typo) in JH's NPD suggested by Wolf is a common one, and the corrected position precesses to 57 46.4, Dec +36 22 33, which lies only 0.4 arcmin northwest of the galaxy listed above, the description fits and there is nothing else nearby, so Wolf's correction is almost certainly correct, and the identification shown above is equally certain.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 4775 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4846 is about 220 to 225 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 230 to 260 million light-years. Given that and its apparent size of about 1.45 by 0.45 arcmin (from the images below), the galaxy is about 90 to 95 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4847 (Tempel list V (#25), 1860 RA 12 51 10, NPD 102 22.6) is "faint, small nebulous star, 9th magnitude star 40 seconds of time preceding (to west) on parallel." The position precesses to RA 12 58 30.3, Dec -13 08 02, only 0.5 arcmin northeast of the galaxy listed above, the description is a perfect fit and there is nothing comparable nearby, so the identification is certain. Usually, only the galaxy is considered to be the NGC object, but since the description specifically states that the object is a nebulous star, and Gottlieb found that all he could see was a suspicion of nebulosity on the southwestern side of the star, there can hardly be any doubt that what Tempel saw was the star first and foremost, and the nebula by chance. As a result, Corwin states that NGC 4847 must be thought of as both the star and the galaxy, and I can't help but agree.
Physical Information: The star is of course merely a foreground object in our own galaxy (based on GAIA's parallax and apparent magnitude, probably a Sun-like star a little over 1800 light-years away). As far as the galaxian part of the NGC object is concerned, based on a recessional velocity relative to the Cosmic Microwave Background radiation of 5140 km/sec (and H₀ = 70 km/sec/Mpc), "NGC 4847" is about 240 million light-years away. Given that and its apparent size of about 0.6 by 0.4 arcmin (from the images below), the galaxy is about 40 to 45 thousand light-years across.

Historical Identification: Per Dreyer, NGC 4848 (= GC 5686, d'Arrest, 1860 RA 12 51 17, NPD 61 00.0) is "pretty faint, small, a little extended." The position precesses to RA 12 58 03.2, Dec +28 14 33, only about 0.5 arcmin west 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 relative to the Cosmic Background Radiation of 7320 km/sec (and H₀ = 70 km/sec/Mpc), a straightforward calculation indicates that NGC 4848 is about 340 million light-years away, in good agreement with redshift-independent distance estimates of about 320 to 350 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 330 million light-years away at the time the light by which we see it was emitted, about 335 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 about 1.55 by 0.45 arcmin (from the images below), the galaxy is about 150 thousand light-years across. The galaxy is listed as having an active galactic nucleus, and as a result, considerable emission by clouds of gas illuminated and excited by the radiation from hot young stars in its nucleus.
Possible Companion "GMP 4475": The galaxy is probably interacting with the small companion to its northeast, GMP 4475, but the distance of that object is unknown, so they may be merely an optical double. However, both objects (and a number of others in the region) are listed as members of Abell 1656, and both have peculiar structures that could be due to an interaction between them, so odds are that they really are physical companions.

Designation Note: HyperLEDA assigned this object a PGC designation, but a search for that designation returns no result, so it is in quotes. The object can be found in NED and SIMBAD by a search for GMP 4475, but for LEDA a successful search requires the incorrect designation ABELL1367:[GP82]4475. (Most obviously incorrect because the object is in Abell 1656, not Abell 1367.)
Physical Information: Since no recessional velocity is available for this object, whether it is a physical companion of NGC 4848 and interacting with it, or merely an optical double is unknown. However, both galaxies are thought to be part of Abell 1656 (though GMP 4475 is mis-assigned to Abell 1367 in LEDA), and the appearance of the two galaxies suggest that they are an interacting pair, and if so the smaller galaxy is also about 330 million light-years away (as discussed in the entry for NGC 4848). If so, its apparent size of about 0.0175 by 0.0105 arcmin (from the image below) corresponds to about 17 thousand light-years.

Historical Identification: Per Dreyer, NGC 4849 (= GC 5687, d'Arrest, (1860 RA 12 51 28, NPD 62 56.1) is "pretty bright, round, brighter middle." The first IC lists a corrected position (per Spitaler) of RA 12 51 24, NPD 62 52. The original NGC position precesses to RA 12 58 16.0, Dec +26 18 28, but there is nothing there, save for a fairly bright galaxy about 5 arcmin to the north. Spitaler's position precesses to RA 12 58 11.9, Dec +26 22 34, about 1.2 arcmin nearly due south of that same galaxy, so that is obviously the nebula he thought d'Arrest observed. The description fits and there is nothing comparable nearby, so the identification is certain. (Note: CGCG originally misidentified this galaxy as IC 838, presumably because of the bastardized identification of IC 838 as "NGC 4849A" (as noted in the entry below), but corrected that mistake with an erratum in volume III. Yet another painful example of why non-standard "letter" designations of NGC/IC objects should never be used.)
Note About Spitaler's Observation: Spitaler's 1892 paper lists observations for 1891 and 1892. Some references incorrectly state that he observed his Nova 61 in 1891, but his paper states that it was observed in 1892; and in the notes at the end of the paper he states that it is probably identical to d'Arrest's NGC 4849, whence Dreyer's IC1 position.
Note About Safford's Observation: Truman Safford's nebular discoveries were not published until 1887, after the main text of the NGC had already been set in type, and though an Appendix to the NGC gave a list of those that had not already been discovered by others (and were therefore included in the First Index Catalogue), no mention is made by Dreyer of any of the 59 NGC objects that others had also observed, either in the NGC or any subsequent publication. However, Safford's "pretty bright" #23's position of (1870) RA 12 52 02.5, Dec +27 06.2 precesses to (2000) RA 12 58 21.2, Dec +26 24 02, only about 1.9 arcmin nearly due east of the galaxy listed above, so there is no doubt that he was indeed the first to discover this object. So Safford's failure to promptly publish his observations cost him a portion of his proper place in astronomical history (or as my father used to say, "He who tooteth not his own horn getteth not tooted").
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 6160 km/sec (and H₀ = 70 km/sec/Mpc), NGC 4849 is about 285 to 290 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 300 to 375 million light-years. Given that and its apparent size of about 1.8 by 1.35 arcmin (from the images below), the galaxy is about 150 thousand light-years across.

Physical Information: Since the object has a perfectly good IC listing, it is pointless and (as shown by the CGCG error noted in the entry for NGC 4849) confusing to call it NGC 4849A; so see IC 838 for anything else.