Historical Identification: Per Dreyer, NGC 1550 (= GC 835, d'Arrest, 1860 RA 04 12 21, NPD 87 56.2) is "very faint, small, round, 13th magnitude star near". The position precesses to RA 04 19 37.8, Dec +02 24 19, well inside the galaxy, so the identification is certain.
Physical Information: Based on a recessional velocity of 3715 km/sec, NGC 1550 is about 170 to 175 million light-years away. Given that and its apparent size of about 1.9 by 1.75 arcmin (from the images below), it is about 95 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1551 (= GC 836 = WH II 464, 1860 RA 04 12 23, NPD 88 55.6) is "faint, very small, round, probably = (GC) 835", GC 835 being NGC 1550, so it was suspected that the two listings referred to the same object at the time of the original publication of the NGC. The problem was the NPD of GC 836, which apparently includes a 1 degree recording error by Herschel. Per Corwin, when d'Arrest observed what became NGC 1550 he could not find Herschel's GC 836, but subsequently realized that if Herschel made a 1 degree error in that object's NPD, then the positions of the two nebulae would be essentially identical. Since the NGC follows the format of the GC, Dreyer had already included a space for both nebulae, so he entered each as if separate; but agreeing with d'Arrest, he noted the presumed equivalence as 'probable' in the original NGC entry, and later adopted the identity as 'definitive'.
Physical Information: Given the duplicate entry, see NGC 1550 for anything else.

Historical Identification: Per Dreyer, NGC 1552 (= GC 837 = JH 313 = WH III 490, 1860 RA 04 13 10, NPD 91 02.3) is "considerably faint, pretty small, a little extended, very gradually brighter middle, 11th magnitude star to southwest".
Physical Information: Apparent size of about 1.45 by 0.95 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 1553 (= GC 838 = JH 2630, (Dunlop #320), 1860 RA 04 13 11, NPD 146 07.8) is "very bright, pretty small, round, gradually much brighter middle, among 3 stars".
Physical Information: Based on a recessional velocity of 1080 km/sec, NGC 1553 is about 50 million light-years away, in good agreement with widely varying redshift-independent distance estimates of 25 to 75 million light-years. Given that and its apparent size of about 7.5 by 6.2 arcmin (from the images below), it is about 110 thousand light-years across. The galaxy is a member of the NGC 1566 group. It is part of a possibly gravitationally bound pair with NGC 1549, which is a little over 11 arcminutes away in the sky, and if at a common distance of about 55 million light-years may be separated by as little as 175 thousand light-years. HST images of the core of NGC 1553 show clouds of gas and dust presumably related to a gravitational interaction with NGC 1549 (perhaps the strongest evidence that they are a pair). Used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type SA(rl)0⁺.

Historical Identification: Per Dreyer, NGC 1554 (= GC 5339, Otto Struve, d'Arrest, 1860 RA 04 13 33, NPD 70 49.0) is a "a magnificent or otherwise interesting object, variable, small, round, with a northern nucleus equivalent to a 13th magnitude star". The first IC adds a note for NGC 1554 that actually applies to NGC 1555, and is posted there. The second IC adds a note applying to both objects, of which these portions apply to NGC 1554: "...Barnard in February and March 1895 found (with the 36-inch refractor) that T Tauri was not, as in 1890, the nucleus of a pretty bright, small nebula; the star was perfectly stellar but involved in a very faint, diffuse nebulous glow; Struve's nebula was not seen, though there was a slight haziness there (MN, lv, pp 442-452, where the whole history of the object is given, to which may be added a reference to a diagram by Otto Struve in 1862, MN xxii, p 242)... Keeler on two photos taken in December 1899 found three very faint, irregular patches, connected by still fainter nebulosity, southwest and west of T Tauri, but clear of the star; no trace of Struve's nebula (ibid, lx p425). Not visible to Burnham around 1907.0 (AN 4209)."
Physical Information: As related in the IC note, NGC 1554 and 1555 have been associated with each other and T Tauri since their discovery. They are undoubtedly variations in the lighting of clouds of gas and dust surrounding T Tauri caused by the movement of denser clouds very close to the star, casting shadows on or allowing shafts of light to reach the surrounding nebulae. The resulting variability in their appearance is the reason that NGC 1555 is called "Hind's Variable Nebula", and the fact that there have been no observations of NGC 1554 since those of Struve and d'Arrest in 1868 makes its "Lost" name equally appropriate. The position given by Dreyer precesses to the one given above, but since nothing has been seen there in nearly a century and a half, NGC 1554 is more a historical curiosity than anything else. LEDA lists NGC 1554 as PGC 5067727 (and as a reflection nebula), but a search of the database for that designation returns no result, which in this case seems appropriate.

Historical Identification: Per Dreyer, NGC 1555 (= GC 839, Hind, 1860 RA 04 13 48, NPD 70 48.8) is "a magnificent or otherwise interesting object, very faint, small, variable (Auwers 20)", the final reference being to a list of nebulae compiled by Arthur von Auwers. The first IC adds a note for NGC 1554 that actually applies to NGC 1555: "Hind's variable nebula, 2 degrees preceding and 40 arcsec south of the variable star T Tauri. Barnard in 1890 found an extremely faint nebula in position 185 degrees, 3/4 arcmin distant from T, which agrees well with Hind's and d'Arrest's observations. Barnard and Burnham also saw T Tauri within a very small condensed nebula (often seen by Tempel). Bigourdan's #144 (a 13th-magnitude nebulous star?) in RA 04 13 56, NPD 70 52, was apparently not seen at the Lick Observatory." The second IC added "Hind's variable nebula. Barnard in February and March 1895 found (with the 36-inch refractor) that T Tauri was not, as in 1890, the nucleus of a pretty bright, small nebula; the star was perfectly stellar but involved in a very faint, diffuse nebulous glow; Struve's nebula was not seen, though there was a slight haziness there (MN, lv, pp 442-452, where the whole history of the object is given, to which may be added a reference to a diagram by Otto Struve in 1862, MN xxii, p 242). In September 1895, on three nights, no trace of Hind's nebula was seen with the 36-inch (ibid, lvi, p 66). Keeler on two photos taken in December 1899 found three very faint, irregular patches, connected by still fainter nebulosity, southwest and west of T Tauri, but clear of the star; no trace of Struve's nebula (ibid, lx p425). Not visible to Burnham around 1907.0 (AN 4209)." As made clear by such extended notes, NGC 1555 and 1554 have been associated with each other and T Tauri since their discovery. They are undoubtedly variations in the lighting of clouds of gas and dust surrounding T Tauri caused by the movement of denser clouds very close to the star, casting shadows on or allowing shafts of light to reach the surrounding nebulae. The resulting variability in their appearance is the reason that NGC 1555 is called "Hind's Variable Nebula". As it happens, the brightness and variation of this and similar nebulae were greatest around the time of their discovery; the IC notes indicate that they were less obvious later on, and they are even less obvious now. Still, observers of such phenomena can always hope to see new activity. NGC 1555 is the brightest part of the reflection nebula just west of T Tauri, and the closest part of a much larger region of nebulosity surrounding the star. Dreyer's position precesses to RA 04 21 57.6, Dec +19 31 22, which is on the southern edge of that brightest part, and that and decades of avid observation following its discovery make the identity certain.
Physical Information: The star and surrounding nebula are about 460 light-years away. Given that and its 0.5 arcmin apparent size, NGC 1555 is about .07 light-years or 4000 AU across; but this is only the size of the brightest and most historically variable part of the nebula, specifically referred to by the NGC listing. As seen in the wide-field images below, surrounding nebular regions extend tens of times further, and the overall size of the nebulosity is much greater. (Note: It may seem odd that an object obviously not a galaxy should have a PGC listing, but there are numerous examples of such listings in the additions to the original PGC. Given the large number of additional objects, some sort of automated system must have been used to identify objects, and entries were created before being checked by a trained observer. At least the catalog entry notes that it is not a galaxy, but a nebula.)

Historical Identification: Per Dreyer, NGC 1556 (= GC 840 = JH 2631, 1860 RA 04 13 57, NPD 140 30.2) is "considerably faint, small, round, very gradually a little brighter middle". The second IC adds (per DeLisle Stewart) "Not round, but extended 165 degrees".
Physical Information: Based on a recessional velocity of 990 km/sec, NGC 1556 is about 45 million light-years away, in good agreement with redshift-independent distance estimates of 44 to 64 million light-years. Given that and its apparent size of about 1.4 by 0.5 arcmin (from the images below), it is not quite 20 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1557 (= GC 841 = JH 2633, 1860 RA 04 14 01, NPD 160 46.4) is "a cluster, very little compressed, about 20 scattered stars". Just south of the magnitude 7.0 star HD 27346
Physical Information: Apparent size of about 15 arcmin (from the image below). LEDA lists the group as PGC 5067592 (and as multiple stars), but a search of the database for that designation returns no result.

Historical Identification: Per Dreyer, NGC 1558 (= GC 842 = JH 2632, 1860 RA 04 14 56, NPD 135 22.0) is "pretty faint, small, extended, gradually brighter middle".
Physical Information: Based on a recessional velocity of 4530 km/sec, NGC 1558 is about 210 million light-years away, in good agreement with redshift-independent distance estimates of 150 to 230 million light-years. Given that and its apparent size of 3.0 by 0.9 arcmin, it is about 185 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1559 (= GC 843 = JH 2634, (Dunlop 264), 1860 RA 04 15 56, NPD 153 07.8) is "very bright, very large, much extended, very gradually pretty much brighter middle, 14th magnitude star attached on north".
Physical Information: Based on a recessional velocity of 1305 km/sec (and H₀ = 70 km/sec/Mpc), NGC 1559 is about 60 million light-years away, in good agreement with redshift-independent distance estimates of 40 to 70 million light-years (the press release for the HST image gives the distance as about 50 million light-years). Given that and its apparent size of 3.5 by 2.0 arcmin, it is about 60 thousand light-years across. The galaxy is apparently all alone in space, without any nearby neighbors, but is still an unusually active object, both in terms of its rate of star-formation and star death (four supernovae have been observed in it since 1984). It is used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type SB(s)cd.

Historical Identification: Per Dreyer, NGC 1560 (Tempel list IX (#1), 1860 RA 04 16 03, NPD 18 25.0) is "very faint, large, extended, 9.3 magnitude star to southwest".
Misidentification Note: LEDA incorrectly lists NGC 1560 as also equal to IC 2062. This is a perpetuation of a misidentification of IC 2062 (which is actually only a star) since disavowed by Corwin, and is only mentioned here as a warning.
Physical Information: NGC 1560's negative radial velocity of -35 km/sec indicates that it is too close for the Universal expansion to affect its motion relative to us, or to provide any hint of its distance. Redshift-independent distance estimates range from 5 to 15 million light-years, with 10 to 12 million light-years being the best current estimate (very close galactically speaking, but definitely not part of the Local Group). Given that and its apparent size of 11.6 by 1.9 arcmin, the galaxy is about 35 thousand light-years across. Used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type Sd/Sm sp.
Maffei Group: This galaxy is part of the Maffei Group of galaxies, which includes NGC 1560, NGC 1569, IC 342, and Maffei 1 and 2).

Historical Identification: Per Dreyer, NGC 1561 (Leavenworth list I (#127), 1860 RA 04 16 38, NPD 106 11.3) is "very faint, very small, a little extended 170°, gradually a little brighter middle, 8th magnitude star 6 seconds to west". The second IC lists a corrected position (per Howe) of RA 04 16 29, NPD 106 10.5.
Physical Information: Apparent size 1.3 by 0.65 arcmin?

Historical Identification: Per Dreyer, NGC 1562 (Leavenworth list I (#128), 1860 RA 04 16 40±, NPD 106 06.3) is "very faint, extremely small, round, gradually a little brighter middle". The second IC lists a corrected position (per Howe) of RA 04 15 26, NPD 106 05.3.
Physical Information: Apparent size 0.45 by 0.45 arcmin?

Historical Identification: Per Dreyer, NGC 1563 (Leavenworth list I (#129), 1860 RA 04 16 40±, NPD 106 04.3) is "extremely faint, very small, round, a little brighter middle, a double nebula with NGC 1564. The second IC lists a corrected position (per Howe) of RA 04 16 32, NPD 106 03.7.
Physical Information: Based on a recessional velocity of 9350 km/sec, a straightforward calculation indicates that NGC 1563 is about 435 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 420 million light-years away at the time the light by which we see it was emitted, about 425 million years ago (the difference between the two numbers being due to the expansion of the intervening space during the light-travel time). Given that and its apparent size of 0.5 by 0.5 arcmin(?), the galaxy is about 60 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1564 (Leavenworth list I (#130), 1860 RA 04 16 40±, NPD 106 04.3) is "extremely faint, very small, round, a little brighter middle, a double nebula with NGC 1563. The second IC lists a corrected position (per Howe) of RA 04 16 39, NPD 106 04.1
Physical Information: Apparent size 0.65 by 0.45 arcmin?

Historical Identification: Per Dreyer, NGC 1565 (Leavenworth list I (#131), 1860 RA 04 16 40±, NPD 106 06.3) is "extremely faint, pretty small, a little extended". The second IC lists a corrected position (per Howe) of RA 04 17 02, NPD 106 04.4.
Physical Information: Based on a recessional velocity of 9195 km/sec, a straightforward calculation indicates that NGC 1565 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 0.95 by 0.85 arcmin(?), the galaxy is about 115 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1566 (= GC 844 = JH 2635, Dunlop 338??, 1860 RA 04 16 52, NPD 145 16.6) is "bright, very large, very gradually then suddenly very much brighter middle, 15 seconds of time diameter in RA." The position precesses to RA 04 19 59.9, Dec -54 56 32, well within the central portion of the galaxy listed above, the description fits and there is nothing else nearby, so the identification is certain.
Discovery Notes: Although Dreyer expressed great uncertainty about Dunlop's observation, Dunlop's description of the nebula and nearby stars exactly matches the galaxy listed here, so there is no doubt that he deserves credit as the first observer. Gottlieb notes that Baracchi used the 48" Great Melbourne Telescope to observe the galaxy, and though most of the observations made with the GMT were never published, Baracchi wrote "the nebulosity is very faint and has a shape almost like the letter S," which appears to be the first mention of its overall shape; hence the mention of his observation in the observers' credits above.
Physical Information: Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background radiation of 1495 km/sec (and H₀ = 70 km/sec/Mpc), NGC 1566 is about 70 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 20 to 70 million light-years. Given that and its apparent size of about 8.5 arcmin for the main galaxy and its bright arms, and about 11.4 by 10.6 arcmin for fainter outer regions (from the images below), the galaxy is about 170 to 175 thousand light-years across, and its outer regions span at least 230 thousand light years. NGC 1566 has an unusually high proportion of exceptionally hot, bright O-type stars (areas in white and pink in the HST image are dominated by such stars), and its exceptionally bright nucleus has led to its classification as a Seyfert galaxy (type Sy1 or Sy1.5, depending on the reference used).
Classification Notes: NGC 1566 is used by the de Vaucouleurs Atlas of Galaxies as an example of type (R₁')SAB(s)bc, which is one of two classifications listed in the NED, but with the addition of a notation indicating a central ring. As shown in the images below, the inner spiral arms do seem to originate at either side of a circular central structure, justifying both the AB classification (somewhere between a barred and unbarred spiral) and the (rs) notation, but since the ring does not have a clearly defined 'edge', I have underlined the "s" to indicate that the spiral structure is more obvious than the central ring. The R' (and subscript 1) indicates that the outer arms form a partial ring surrounding the entire galaxy.

Historical Identification: Per Dreyer, NGC 1567 (= GC 845 = JH 2636, 1860 RA 04 17 09, NPD 138 35.4) is "faint, small, round, brighter middle".
Physical Information: Apparent size of about 1.5 by 1.5 arcmin (from the images below).

Historical Identification: Per Dreyer, NGC 1568 (Swift list V (#60), 1860 RA 04 17 14, NPD 91 04.8) is "extremely faint, very small, round, nearly between 2 stars". Swift would not have noticed PGC 15034, the fainter companion of PGC 15042, but since they are physically interacting NGC 1568 is usually (incorrectly) considered to be the pair of galaxies.
Physical Information: Based on an average recessional velocity of 4640 km/sec (there is only a difference of 30 km/sec between the separate values), NGC 1568 is about 215 million light-years away. Given that, the 1.65 by 1.35 arcmin apparent size of PGC 15042 corresponds to about 100 thousand light-years. The 3.8 arcmin overall apparent size of the pair of galaxies, counting the extended tail caused by a recent collision or ongoing gravitational interaction, corresponds to about 240 thousand light-years. LEDA lists NGC 1568 as the pair of galaxies, with the designation PGC 3166885; but a search of the database for that designation returns no result. It lists both PGC 15042 and PGC 15034 as NGC 1568: (meaning, as part of the NGC object).

Historical Misidentification: As noted in the entry for NGC 1568, PGC 15034 is usually listed as part of that NGC object; but it is too faint for Swift to have seen, so although physically interacting with NGC 1568, it should not be considered to be part of it.
Physical Information: About 0.4 by 0.25 arcmin? For now, see NGC 1568 for images.

Historical Identification: Per Dreyer, NGC 1569 (= GC 847 = WH II 768, 1860 RA 04 17 36, NPD 25 28.1) is "pretty bright, small, a little extended, brighter nucleus and middle, 9.5 magnitude star 1 arcmin to north".
Physical Information: NGC 1569 is one of the nearest starburst irregular galaxies (it is a member of the IC 342/Maffei Group). It underwent a surge of star production about 25 million years ago, lasting for around 20 million years. The most massive stars produced during this time had very short lives, and almost immediately began a surge of supernova explosions that gives us an unusually detailed view of star birth and death. The galaxy's negative radial velocity (-105 km/sec) shows that it is too close for the Universal expansion to have an effect on its motion relative to us, so its distance cannot be determined from its 'recessional' velocity. Redshift-independent distance estimates range from 5 to 20 million light-years, with 11 million light-years being the current "best" estimate. Given that and its apparent size of 3.7 by 1.8 arcmin, the galaxy is about 12 thousand light-years across. Used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type IB(s)m. Used by the Arp Atlas as an example of a galaxy with irregularities, absorption, and resolution.
Maffei Group: This galaxy is part of the Maffei Group of galaxies, which includes NGC 1560, NGC 1569, IC 342, and Maffei 1 and 2).

Historical Identification: Per Dreyer, NGC 1570 (= GC 846 = JH 2637, 1860 RA 04 17 42, NPD 133 47.5) is "faint, small, round, gradually brighter middle". Herschel's declination for JH 2637 was off by 10 arcmin, hence the double listing. The description and RA confirm the identity of the two entries. However, because of that error it is often listed as NGC 1571, instead of NGC 1570
Physical Information: Apparent size of about 2.8 by 1.7 arcmin, including its fainter outer extensions.

Historical Identification: Per Dreyer, NGC 1571 (= GC 848 = JH 2638, 1860 RA 04 17 46, NPD 133 57.0) is "very faint, small, round, gradually brighter middle, double star to northeast".
Physical Information: Given the duplicate entry, see NGC 1570 for anything else.

Historical Identification: Per Dreyer, NGC 1572 (= GC 849 = JH 2639, 1860 RA 04 17 59, NPD 130 55.1) is "pretty faint, small, round, 13th magnitude star 1 arcmin to northeast".
Physical Information: Based on a recessional velocity of 6110 km/sec, NGC 1572 is about 285 million light-years away, a bit farther than redshift-independent distance estimates of 190 to 265 million light-years. Given that and its apparent size of 2.8 by 1.2 arcmin(?), it is about 220 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1573 (Tempel list IX (#2), 1860 RA 04 18 16, NPD 17 04.0) is "very faint, small, magnitude 9.5 star to east". This precesses to RA 04 34 51.1, Dec +73 14 33, about 1.5 arcmin southwest of the galaxy listed above (just beyond its faint outer region), the description fits and there is nothing comparable nearby, so the identification is certain.
Physical Information: The apparent size of the bright inner region is about 1.15 by 0.8 arcmin, and that of the faint outer region is about 2.6 by 1.4 arcmin (both from the images below). Those numbers correspond to a classification between E3 and E5, whence the "type E4?" shown above. Based on a recessional velocity of 4220 km/sec (and H₀ = 70 km/sec/Mpc), the galaxy is about 195 million light-years away, in good agreement with redshift-independent distance estimates of about 165 to 305 million light-years. Given that and the apparent sizes already listed, the bright inner region is about 65 thousand light-years across, and the faint outer region spans about 150 thousand light-years..

Historical Identification:
Physical Information: Based on a recessional velocity of 4500 km/sec, PGC 16052 is about 210 million light-years away. Given that and its apparent size of about 1.55 by 1.25 arcmin (based on the images below), it is about 95 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1574 (= GC 850 = JH 2640, 1860 RA 04 19 13, NPD 147 17.9) is "pretty bright, small, round, pretty gradually brighter middle, 2 small (faint) stars to southeast".
Physical Information: Based on a recessional velocity of 1040 km/sec, NGC 1574 is about 50 million light-years away, in good agreement with redshift-independent distance estimates of 45 to 65 million light-years. Given that and its apparent size of 4.0 by 3.6 arcmin(?), it is about 65 thousand light-years across. Used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type SB0^-.

Historical Identification: Per Dreyer, NGC 1575 (Muller list II (#395), 1860 RA 04 19 17, NPD 100 25.2) is "very faint, pretty small, round, 9.5 magnitude star 2 arcmin to south". Swift's RA is nearly correct, but his declination is off. Muller's declination is OK, but his RA is too small. The two errors led to two entries, but the descriptions are sufficiently similar that Howe noted the identity of the two entries in a 1900 paper; hence Dreyer's second IC note (per Howe) that NGC 1575 is the same as NGC 1577; so the identity has been known for more than a century. Since both entries were "off", it seems appropriate to use the NGC number for the earlier discovery, and that is what happened.
Discovery Notes: (and note to self: all "1886" dates for Stone's list II must be prior to the date of submission, which I think was Oct 12; need to check and fix all entries ASAP)
Physical Information: So this entry will deal only with historical information; for anything else see NGC 1577.

Historical Identification: Per Dreyer, NGC 1576 (= GC 851 = JH 314 = WH III 587, 1860 RA 04 19 24, NPD 93 57.0) is "extremely faint, brighter middle, between 2 stars".
Physical Information: Apparent size 1.1 by 0.7 arcmin?

Historical Identification: Per Dreyer, NGC 1577 (Swift list III (#29), 1860 RA 04 19 39, NPD 100 26.0) is "very faint, pretty large, round, a little brighter middle, star near to south".
Physical Information: Based on a recessional velocity of 9335 km/sec, NGC 1577 is about 435 million light-years away (need to take relativistic correction into account). Given that and its apparent size of 1.4 by 1.2 arcmin, it is about 175 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1578 (= GC 852 = JH 2641, 1860 RA 04 20 12, NPD 141 55.2) is "pretty faint, small, round, brighter middle".
Physical Information: Based on a recessional velocity of 6180 km/sec, NGC 1578 is about 290 million light-years away (a second recessional velocity measurement of 6800 km/sec would suggest a distance of 315 million light-years). Given that and its apparent size of 1.2 by 1.1 arcmin(?), it is about 100 to 110 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1579 (= GC 853 = JH 315 = WH I 217, 1860 RA 04 21 03, NPD 55 01.9) is "pretty bright, very large, irregularly round, much brighter middle, 8th magnitude star 2 arcmin distant at position angle 350°".
Physical Information: Apparent size 12 by 8 arcmin? Listed in LEDA as PGC 3517587 (and as a reflection nebula), but a search of the database for that designation returns no result.

Historical Identification: Per Dreyer, NGC 1580 (= GC 5340, Stephan list VIII (#14), 1860 RA 04 21 25, NPD 95 29.6) is "very faint, very small, round, mottled but not resolved".
Physical Information: Based on a recessional velocity of 4265 km/sec, NGC 1580 is about 200 million light-years away. Given that and its apparent size of 1.05 by 0.9 arcmin, it is about 60 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1581 (= GC 854 = JH 2642, 1860 RA 04 21 37, NPD 145 15.8) is "faint, small, extended, gradually a little brighter middle".
Physical Information: Apparent size 1.8 by 0.7 arcmin?

Historical Identification: Per Dreyer, NGC 1582 (= GC 855 = WH VIII 70, 1860 RA 04 22 09, NPD 46 27.6) is "a cluster, very large, pretty rich, a little compressed, stars large (bright)".
Physical Information: Apparent size 24 arcmin? Listed in LEDA as PGC 3517890 (and as a cluster), but a search of the database for that designation returns no result.

Historical Identification: Per Dreyer, NGC 1583 (Leavenworth list I (#132), 1860 RA 04 22 40, NPD 107 56.1) is "faint, very small, round, suddenly brighter middle and nucleus". The second IC lists a corrected RA (per Howe) of 04 22 05.
Physical Information: Apparent size of 0.7 by 0.7 arcmin?

Historical Identification: Per Dreyer, NGC 1584 (Leavenworth list I (#133), 1860 RA 04 22 40,, NPD 107 51.1) is "faint, extremely small, round, suddenly brighter middle and nucleus". The second IC lists a corrected RA (per Howe) of 04 21 54.
Physical Information: Apparent size 0.6 by 0.6 arcmin?

Historical Identification: Per Dreyer, NGC 1585 (= GC 856 = JH 2643, 1860 RA 04 22 58, NPD 132 27.7) is "pretty faint, small, round, gradually brighter middle, 12th magnitude star at position angle 287.8°".
Physical Information: Based on a recessional velocity of 4655 km/sec, NGC 1585 is about 215 million light-years away. Given that and its apparent size of 1.2 by 0.7 arcmin(?), it is about 75 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1586 (= GC 857, d'Arrest, 1860 RA 04 23 05, NPD 90 50.1) is "very faint, irregular figure, very little brighter middle, between a double star and a 14th magnitude star".
Physical Information: Based on a recessional velocity of 3570 km/sec, NGC 1586 is about 165 million light-years away, in good agreement with redshift-independent distance estimates of 140 to 175 million light-years. Given that and its apparent size of 1.7 by 0.9 arcmin(?), it is about 80 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1587 (= GC 858 = JH 316 = WH II 8, 1860 RA 04 23 28, NPD 89 38.8) is "faint, pretty small, round, mottled but not resolved, western of double nebula", the other being NGC 1588.
Physical Information: Apparent size 1.7 by 1.4 arcmin? Probably paired with NGC 1588.

Historical Identification: Per Dreyer, NGC 1588 (= GC 859 = JH 317 = WH II 9, 1860 RA 04 23 32, NPD 89 38.6) is "faint, very small, round, mottled but not resolved, eastern of double nebula", the other being NGC 1587.
Physical Information: Apparent size 1.1 by 0.6 arcmin? Probably paired with NGC 1587.

Historical Identification: Per Dreyer, NGC 1589 (= GC 860 = JH 318 = WH II 7, 1860 RA 04 23 33, NPD 89 26.6) is "faint, pretty large, a little extended 132°, a star 80 arcsec distant at position angle 42°". The position precesses to RA 04 30 45.4, Dec +00 51 50, right on the galaxy listed above, the description fits perfectly and there is nothing else nearby, so the identification is certain.
Discovery Note: I have added Mitchell's observation because he noted (using Lord Rosse's 72-inch "Leviathan") that "the preceding (western) edge seems black and sharp compared to its following (eastern) edge." This means that he noticed the dust lane obscuring the western side of the galaxy.
Physical Information: Based on a recessional velocity relative to the Cosmic Microwave Background of 3725 km/sec, NGC 1589 is about 170 to 175 million light-years away, in reasonable agreement with redshift-independent distance estimates of about 150 to 170 million light-years. Given that and its apparent size of about 4.25 by 1.15 arcmin (from the images below), it is about 215 thousand light-years across. Not long ago astronomers observed effects caused by the disruption and absorption of a star by the supermassive black hole at the center of this galaxy; the HST is now being used to look for debris thrown out of the accretion disk created by the absorption of the star, to see how theories about such events square with direct evidence of their results. Even supermassive black holes can't just pull stars into themselves, but being in the center of the galaxy, they are surrounded by tens of billions of stars, and once in a while one of them will accidentally pass too close to the black hole and be torn apart by its gravity, then fall through the black hole's event horizon, into its interior. During that process, a dense accretion disk forms around the black hole, and all sorts of extremely energetic events can occur as a result, as previously observed.

Historical Identification: Per Dreyer, NGC 1590 (= GC 5341, d'Arrest, 1860 RA 04 23 38, NPD 82 40.0) is "faint, small, 12th magnitude star to northeast".
Physical Information: Based on a recessional velocity of 3895 km/sec, NGC 1590 is about 180 million light-years away. Given that and its apparent size of 0.9 by 0.7 arcmin(?), it is about 50 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1591 (= GC 861 = JH 2644, 1860 RA 04 23 49, NPD 117 00.8) is "pretty faint, pretty small, round, gradually brighter middle".
Physical Information: Based on a recessional velocity of 4115 km/sec, NGC 1591 is about 190 million light-years away, in reasonable agreement with redshift-independent distance estimates of 140 to 180 million light-years. Given that and its apparent size of 1.2 by 0.8 arcmin(?), it is about 65 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1592 (= GC 862 = JH 2645, 1860 RA 04 23 53, NPD 117 16.0) is "very faint, very small". The second IC adds "Only faint stars seen by Howe". The position precesses to RA 04 29 35.3, Dec -26 57 29, but there is nothing there, which is presumably why Howe saw only faint stars near Herschel's position. However, given the fact that it is listed by Herschel as being nearly due south of and fainter than GC 681 = NGC 1591, it seems appropriate to look for a somewhat fainter galaxy than NGC 1591 somewhere to its south; and the galaxy listed above fits the description, so despite being nearly half a degree further south its identification as NGC 1592 is considered reasonably certain (sufficiently so that although some references list NGC 1592 as nonexistent, most identify it as PGC 15292).
Additional Note: Presuming that NGC 1592 is the object listed above, Herschel would only have been able to see its brighter eastern part (PGC 15292), and as a result that is the usual identification for NGC 1592. However, the complex structure shown in the images below consists of PGC 15292 and PGC 15285, so I have chosen to include both of them not only in this discussion but also in the title and description for this entry.
Physical Information: Based on a recessional velocity of 945 km/sec, NGC 1592 is about 45 million light-years away, in fair agreement with a single redshift-independent distance estimate of 30 million light-years. Since both distances are uncertain (the Hubble distance due to the possible presence of "peculiar" or non-Hubble redshift motions of a few tens of km/sec (or more), and the redshift-independent distance due to inherent uncertainties in the method used to produce what is literally an "estimate" of the distance), it seems appropriate to assign an approximate distance of about 40 million light-years to the system. Given that, the apparent size of the overall structure of about 1.6 by 0.55 arcmin corresponds to about 20 thousand light-years, making it a relatively small galaxy. NGC 1592 might best be described as a single irregular galaxy, but it has been suggested that it is the result of the merger of at least two formerly independent galaxies, seen at a fairly late stage in their merger, in which case some of the brighter regions in the eastern part of the structure may represent the nuclei of the original galaxies, and the irregular appearance of the galaxy's halo is consistent with such a merger. However, the reddish blobs near the center of the structure are definitely large star-forming regions, and even the brighter regions to their east may simply be much more active star-forming regions, in which case the galaxy may not be the result of a recent merger, but simply a "late bloomer" in terms of its history of star formation (as appears to be the case for many "dwarf" irregular galaxies).

Historical Identification: Per Dreyer, NGC 1593 (= GC 5342, Marth #97, 1860 RA 04 23 56, NPD 89 44) is "very faint". The position precesses to RA 04 31 07.5, Dec +00 34 22, but there is nothing there, and apparently no one realized that it might be the same as NGC 1608 before Corwin, so it was a "lost" object for the best part of a century. However, since the solution appears to be a simple one (Marth's RA was 1 minute too small, which is a not uncommon transcription error), the identity of the two listings seems reasonably certain.
Physical Information: Apparent size of about 1.6 by 0.6 arcmin?

Historical Identification: Per Dreyer, NGC 1594 (Swift list V (#61), 1860 RA 04 24 17, NPD 96 06.5) is "very faint, pretty small". Swift's RA is wrong, but the second IC lists a corrected RA (per Howe) of 04 23 59. The corrected position precesses to RA 04 30 51.3, Dec -05 48 07, which is well inside the galaxy, so the identification is certain.
Physical Information: Based on a recessional velocity of 4330 km/sec, NGC 1594 is about 200 million light-years away, in fair agreement with redshift-independent distance estimates of 220 to 250 million light-years. Given that and its apparent size of 1.8 by 1.3 arcmin(?), the galaxy is about 110 thousand light-years across.

Physical Information: The Carafe Group is a triplet of three galaxies that have similar recessional velocities (and are therefore presumably at comparable distances) in the same region of Caelum. It consists of PGC 15172, NGC 1595 and NGC 1598. Based on a recessional velocity of 4945 km/sec, PGC 15172 is about 230 million light-years away. Similar calculations indicate a distance for NGC 1595 of about 225 million light-years, and for NGC 1598 of about 240 million light-years, suggesting a common distance (if the triplet really is a physical group) of about 230 million light-years. Given that and its apparent size of 2.1 by 1.8 arcmin, PGC 15172 is about ? thousand light-years across. A Seyfert galaxy (type Sy 2). Perhaps a polar ring galaxy (that is, one in which a ring circles the galaxy perpendicular to the plane of its disk).

Historical Identification: Per Dreyer, NGC 1595 (= GC 863 = JH 2646, 1860 RA 04 24 25, NPD 138 07.1) is "very faint, small, round, brighter middle".
Physical Information: The Carafe Group is a triplet of three galaxies that have similar recessional velocities (and are therefore presumably at comparable distances) in the same region of Caelum. It consists of the Carafe Galaxy (PGC 15172), NGC 1595 and NGC 1598. Based on a recessional velocity of 4810 km/sec, NGC 1595 is about 225 million light-years away. Similar calculations indicate a distance for PGC 15172 of about 230 million light-years, and for NGC 1598 of about 240 million light-years, suggesting a common distance (if the triplet really is a physical group) of about 230 million light-years. (This is far greater than redshift-independent distance estimates for NGC 1595 of only 92 to 108 million light-years, and cannot be reconciled with them; and I have chosen to ignore the redshift-independent estimates, on the basis of the prevailing view that NGC 1595 is part of the Carafe Group.) Given that and its apparent size of 1.5 by 1.05 arcmin, NGC 1595 should be about 100 thousand light-years across.

Historical Identification: Per Dreyer, NGC 1596 (= GC 864 = JH 2648, 1860 RA 04 24 35, NPD 145 20.3) is "bright, pretty large, much extended 15°, suddenly much brighter middle, western of 2", the other being NGC 1602.
Physical Information: Based on a recessional velocity of 1510 km/sec, NGC 1596 is about 70 million light-years away, a bit further than redshift-independent distance estimates of 44 to 58 million light-years. Given that and its apparent size of 4.4 by 1.1 arcmin, it is about 90 thousand light-years across. Used by the de Vaucouleurs Atlas of Galaxies as an example of galaxy type S0^- sp.

Historical Identification: Per Dreyer, NGC 1597 (Ormond Stone list I (#134) 1860 RA 04 24 35, NPD 101 35.0) is "extremely faint, very small, round, gradually brighter middle".
Physical Information: Apparent size 0.9 by 0.7 arcmin?

Historical Identification: Per Dreyer, NGC 1598 (= GC 865 = JH 2647, 1860 RA 04 24 36, NPD 138 05.4) is "faint, small, round, brighter middle".
Physical Information: The Carafe Group is a triplet of three galaxies that have similar recessional velocities (and are therefore presumably at comparable distances) in the same region of Caelum. It consists of the Carafe Galaxy (PGC 15172), NGC 1595 and NGC 1598. Based on a recessional velocity of 5130 km/sec, NGC 1598 is about 240 million light-years away, in fair agreement with redshift-independent distance estimates of 135 to 220 million light-years. Similar calculations indicate a distance for PGC 15172 of about 230 million light-years, and for NGC 1595 of about 225 million light-years, suggesting a common distance (if the triplet really is a physical group) of about 230 million light-years. Given that and its apparent size of 1.4 by 0.8 arcmin, NGC 1598 is about 95 thousand light-years across. Like the Carafe Galaxy, NGC 1598 has an extended system of peculiar arms and jets (faintly visible in the images below) that cover half again the area of the main galaxy (about 2.1 by 1.5 arcmin), or about 140 thousand light-years.

Historical Identification: Per Dreyer, NGC 1599 (Stephan list XII (#29), 1860 RA 04 24 43, NPD 94 53.5) is "very faint, very small, round, very little brighter middle".
Physical Information: Based on a recessional velocity of 4055 km/sec, NGC 1599 is about 190 million light-years away. Given that and its apparent size of 0.9 by 0.8 arcmin(?), it is about 50 thousand light-years across.