Historical Identification: Per Dreyer, NGC 6850 (= GC 4530 = JH 3806, 1860 RA 19 52 28, NPD 145 13.8) is "very faint, small, round, brighter middle".
Physical Information: Apparent size 2.1 by 1.1? arcmin

Historical Identification: Per Dreyer, NGC 6851 (= GC 4531 = JH 3807, 1860 RA 19 53 19, NPD 138 39.2) is "pretty faint, small, very little extended, pretty suddenly brighter middle".
Physical Information: Apparent size 2.0 by 1.5? arcmin

Warning About Non-Standard Designations: As the double listing for this object shows, there is nothing standard about "non-standard" letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Since also listed as NGC 6861A, see that entry for anything else.

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.1 by 0.2? arcmin

Historical Identification: Per Dreyer, NG 6852 (= GC 5949, Marth #404, 1860 RA 19 53 28, NPD 88 39) is "a faint nebula, among stars".
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Apparent size 0.47? arcmin

Historical Identification: Per Dreyer, NGC 6853 (= GC 4532 = JH 2060, M 27, 1860 RA 19 53 33, NPD 67 39.6) is "a magnificent or otherwise interesting object, very bright, very large, binuclear, irregularly extended (Dumbbell)".
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Apparent size 6.7? arcmin

Historical Identification: Per Dreyer, NGC 6854 (= GC 4533 = JH 3808, 1860 RA 19 54 41, NPD 144 45.7) is "faint, small, very little extended, gradually a little brighter middle."
Physical Information: Apparent size 2.0 by 1.3? arcmin; GAIA agrees with the identification as a pair
NED 20.2 - 76.7 Mpc, SAB(s)0- pec, 2.0 x 1.3 arcmin, 13.2b, 3K Vr 5607 km/sec, only one position given
Steinicke lists as only a single galaxy (PGC 64080); Corwin as a pair

Physical Information: NED 16.1b, 3K Vr 5818 km/sec, so quite possibly an actual companion

Historical Identification: Per Dreyer, NGC 6855 (= GC 4534 = JH 3809, 1860 RA 19 55 32, NPD 146 47.0) is "pretty faint, small, round".
Physical Information: Apparent size 1.5 by 1.3? arcmin
NED (R')SB0^+(rs)?, R)SB(rl)0^+, 3K Vr 4228 km/sec

Physical Information: LEDA B 15.3; NED 3K 15470 km/sec, z 0.05160242856. Since it is at least three times further from us than NGC 6855, it is only a distant background object (an optical double).

Historical Identification: Per Dreyer, NGC 6856 (= GC 4535 = JH 2063, 1860 RA 19 56 09, NPD 34 15.2) is "a cluster, pretty small, pretty much compressed, irregularly round, stars from 12th to 16th magnitude".
Physical Information: Apparent size 3.0? arcmin. Possibly a physically connected group, or open cluster.

Historical Identification: Per Dreyer, NGC 6857 (= GC 4536 = JH 2062 = WH III 144, 1860 RA 19 56 24, NPD 56 51.6) is "faint, among Milky Way stars".
Physical Information: Apparent size 0.63? arcmin. (Steinicke notes not a planetary nebula)

Historical Identification: Per Dreyer, NGC 6858 (= GC 4537 = JH 2061, 1860 RA 19 56 24, NPD 79 07.4) is "a cluster, considerably large, extended, pretty rich, stars from 13th magnitude".
Physical Information: Apparent size 5.0? arcmin

Historical Identification: Per Dreyer, NGC 6859 (= GC 4538, G. P. Bond (24, HN 6), 1860 RA 19 56 40, NPD 89 56.7) is "a very small cluster, 10th magnitude star 1 second of time to west, 1' 29" to south (Auwers 46)", Auwers 46 meaning that John Herschel obtained the information about the discovery from Auwers' catalog.
Physical Information:

Historical Identification: Per Dreyer, NGC 6860 (= GC 4539 = JH 3810, 1860 RA 19 56 41, NPD 151 29.5) is "faint, pretty small, gradually brighter middle".
Physical Information: Apparent size 1.3 by 0.8? arcmin

Historical Identification: Per Dreyer, NGC 6861 (= GC 4540 = JH 3811, Dunlop 425, 1860 RA 19 57 05, NPD 138 46.1) is "bright, small, considerably extended, gradually pretty much brighter middle".
Physical Information: Apparent size 3.0 by 2.0? arcmin

Warning About Non-Standard Designations: As the double listing for this object shows, there is nothing standard about "non-standard" letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.3 by 0.6? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.2 by 0.3? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.2 by 0.5? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 2.1 by 0.7? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.4 by 0.3? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.6 by 0.3? arcmin

Historical Identification: Per Dreyer, NGC 6862 (= GC 4541 = JH 3812, 1860 RA 19 57 40, NPD 146 47.3) is "faint, small, a little extended, gradually a little brighter middle".
Physical Information: Apparent size 1.6 by 1.3? arcmin

Historical Identification: Per Dreyer, NGC 6863 (= GC 4542 = JH 2065, 1860 RA 19 57 47, NPD 93 57.0) is "a cluster, small, very much compressed, stars of 19th magnitude".

Historical Identification: Per Dreyer, NGC 6864 (= GC 4543 = JH 2064, Méchain, M 75, 1860 RA 19 57 49, NPD 112 19.0) is "a globular cluster, bright, pretty large, round, very much brighter middle and bright nucleus, partially resolved (some stars seen)".
Physical Information: Over 100 light-years across, and 60 to 100 thousand light-years away (apparent size 6.8? arcmin).

Historical Identification: Per Dreyer, NGC 6865 (= GC 5950, Marth #405, 1860 RA 19 58 20, NPD 99 26) is "faint, small, extended".
Physical Information: Apparent size 0.8 by 0.6? arcmin

Historical Identification: Per Dreyer, NGC 6866 (= GC 4544 = JH 2066 = WH VII 59, (Caroline Herschel), 1860 RA 19 59 11, NPD 46 23.8) is "a cluster, large, very rich, considerably compressed".
Discovery Notes: Although Caroline Herschel discovered this cluster in 1783, William Herschel's published paper only lists his own (later) observation of the cluster; hence her absence in Dreyer's entry for this object, and her inclusion here in parentheses.
Physical Information: Apparent size 7.0? arcmin

Historical Identification: Per Dreyer, NGC 6867 (= GC 4545 = JH 3813, 1860 RA 19 59 32, NPD 145 11.1) is "most extremely faint, large, pretty much extended".
Physical Information: Apparent size 2.0 by 0.7? arcmin

Historical Identification: Per Dreyer, NGC 6868 (= GC 4546 = JH 3814, 1860 RA 19 59 41, NPD 138 46.4) is "very bright, small, round, pretty gradually very much brighter middle".
Physical Information: Apparent size 3.6 by 2.8? arcmin
3K Vr 2716 km/sec

Note About PGC Designation: Although HyperLEDA assigns the PGC designation shown above to this object, a search of the database for that designation returns no result; the 2MASX designation must be used for such a search to succeed, hence the quotes placed around the PGC designation (the same thing is true for a search of the NED).
Physical Information: 3K Vr 2714 km/sec; almost certainly a physical pair

Historical Identification: Per Dreyer, NGC 6869 (Swift list II (#83) and IV (#??), 1860 RA 19 59 48, NPD 24 09.1) is "pretty bright, pretty small, round".
Physical Information: Apparent size 1.6 by 1.3? arcmin

Historical Identification: Per Dreyer, NGC 6870 (= GC 4547 = JH 3815, 1860 RA 19 59 58, NPD 138 41.3) is "considerably faint, considerably small, extended 90°, gradually brighter middle".
Physical Information: Apparent size 2.6 by 1.3? arcmin

Physical Information: NED 3K Vr 17208 km/sec, z 0.05739968. A far more distant galaxy, so only an "optical double"

Historical Identification: Per Dreyer, NGC 6871 (= GC 4548 = JH 2067, Struve 2630, 1860 RA 20 00 38, NPD 54 37.2) is "a cluster, stars large and small, double star involved".
Discovery Notes: For more than a century it was thought that Struve was the first to observe this object; but per Steinicke, Herschel had already observed the cluster (but not recorded it as such) during his early studies of double stars, whence the date of observation shown above.
Physical Information: Apparent size 30? arcmin

Historical Identification: Per Dreyer, NGC 6872 (= GC 4549 = JH 3816, 1860 RA 20 02 03, NPD 161 11.9) is "faint, pretty small, a little extended, gradually a little brighter middle, 9th magnitude star 10.5 seconds of time to west, 1st of 4", the others being NGC 6876, 6877 and 6880.
Physical Information: Based on a recessional velocity of 4555 km/sec, NGC 6872 is about 210 million light-years away. Given that and its apparent size of 7.0 by 1.0 arcmin, it is about 430 thousand light-years across. This is the extent of its wide-spread arms, which are caused by its gravitational interaction with lenticular galaxy IC 4970; the central portion of the galaxy, which is only 2.0 by 0.9 arcmin, is only about 125 thousand light-years across. Still, our own Milky Way galaxy is only about 100 thousand light-years across, so NGC 6872 is an unusually large galaxy (in fact, according to a 2013 NASA report, perhaps the largest known spiral galaxy).

Historical Identification: Per Dreyer, NGC 6873 (= GC 4550 = JH 2068, Struve 2631, 1860 RA 20 02 05, NPD 69 17.9) is "a cluster, a little compressed, stars from 10th to 13th magnitude, double star involved".
Physical Information: Apparent size 14? arcmin

Historical Identification: Per Dreyer, NGC 6874 (= GC 4551 = JH 2069 = WH VIII 86, 1860 RA 20 02 44, NPD 52 09.6) is "a cluster, poor, a little compressed".
Physical Information: Apparent size 7.0? arcmin

Historical Identification: Per Dreyer, NGC 6875 (= GC 4552 = JH 3819, 1860 RA 20 03 15, NPD 136 34.4) is "faint, very small, round, very gradually much brighter middle, 7th magnitude star to northeast". The second IC adds "7th magnitude star 3 arcmin to southwest, not northeast (DeLisle Stewart). h. in Cape Obs. has southeast", "h." meaning John Herschel (JH in this catalog).
Physical Information: Apparent size 2.4 by 1.4? arcmin.

Physical Information: NED 3K Vr 3206 km/sec

Note About PGC Designation: Although HyperLEDA assigns the PGC designation shown above to this object, a search of the database for that designation returns no result; the 2MASX designation must be used for such a search to succeed, hence the quotes placed around the PGC designation (the same thing is true for a search of the NED).
Physical Information: NED 16.7b, 3K Vr 9203 km/sec, z 0.030697988. A far more distant galaxy, so only an "optical double"

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 2.7 by 0.4? arcmin

Historical Identification: Per Dreyer, NGC 6876 (= GC 4553 = JH 3817, 1860 RA 20 03 28, NPD 161 17.1) is "pretty bright, small, round, extremely small (faint) star to southeast, 2nd of 4", the others being NGC 6872, 6877 and 6880.
Physical Information: Apparent size 2.7 by 2.4? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one. (In this case, where there is already a perfectly good IC designation, the use of the non-standard "NGC 6876A" is even more egregious.)
Physical Information: Since there is a perfectly good IC designation, see IC 4945for anything else.

Historical Identification: Per Dreyer, NGC 6877 (= GC 4554 = JH 3818, 1860 RA 20 03 45, NPD 161 17.2) is "very faint, very small, round, 3rd of 4", the others being NGC 6872, 6876 and 6880.
Physical Information: Apparent size 1.1 by 0.6? arcmin

Historical Identification: Per Dreyer, NGC 6878 (= GC 4555 = JH 3821, 1860 RA 20 04 03, NPD 134 56.5) is "very faint, pretty large, round, gradually a little brighter middle".
Physical Information: Apparent size 1.6 by 1.3? arcmin

Warning About Non-Standard Designations: There are no standards for letter designations for galaxies. This often causes confusion, and occasionally results in data for one object being incorrectly assigned to a completely different object. Because of this, such designations should never be used, except for warnings such as this one.
Physical Information: Apparent size 1.8 by 0.8? arcmin

Physical Information:

Historical Identification: Per Dreyer, NGC 6879 (Pickering (HN 55), Copeland, 1860 RA 20 04 04, NPD 73 29.3) is "a planetary nebula, stellar, equivalent to 10th-magnitude star". The position precesses to RA 20 10 26.6, Dec +16 55 22, dead center on the star in question, so the identification is certain. As in the case of Pickering's other "stellar" planetaries, NGC 6879 is only a few arcsec across, and appears almost perfectly stellar even under high magnification; however, using a filter (such as an OIII filter) that blocks out all radiation save that emitted by clouds of interstellar gas it is possible to "blink" the object. Switching the filter in and out causes stars, which emit only a small portion of their light at the wavelengths passed by the filter, look markedly fainter when the filter is in place, while nebulae look nearly as bright with the filter as without.
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Apparent size 9 arcsec.

Historical Identification: Per Dreyer, NGC 6880 (= GC 4556 = JH 3820, 1860 RA 20 04 41, NPD 161 17.1) is "faint, small, round, mottled but not resolved, very small (faint) star attached, 4th of 4", the others being NGC 6872, 6876 and 6877.
Physical Information: Apparent size 2.0 by 0.9? arcmin

Historical Identification: Per Dreyer, NGC 6881 (Pickering (HN 44), 1860 RA 20 05 43, NPD 53 00) is "a planetary nebula, stellar". The position precesses to RA 20 10 52.9, Dec +37 24 50, within 0.1 arcmin of the star in question, so the identification is certain. As in the case of Pickering's other "stellar" planetaries (such as NGC 6879), NGC 6881 is only a few arcsec across and appears almost perfectly stellar even under high magnification; however, using a filter (such as an OIII filter) which blocks out all radiation save that emitted by clouds of interstellar gas, it is possible to "blink" the object. Switching the filter in and out causes stars, which emit only a small portion of their light at the wavelengths passed by the filter, look markedly fainter when the filter is in place, while nebulae look nearly as bright with the filter as without.
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Apparent size 16? arcsec.

Historical Identification: Per Dreyer, NGC 6882 (= GC 4557 = WH VIII 22, 1860 RA 20 05 58, NPD 63 42.6) is "a cluster, poor, a little compressed".
Physical Information: Apparent size 2.0? arcmin.

Historical Identification: Per Dreyer, NGC 6883 (= GC 4558 = JH 2070, 1860 RA 20 05 59, NPD 54 34.3) is "a cluster, pretty rich, double star involved".
Physical Information: Apparent size 35? arcmin

Historical Identification: Per Dreyer, NGC 6884 (Copeland, 1860 RA 20 05 59, NPD 43 57.2) is "a planetary nebula, stellar". The position precesses to RA 20 10 23.6, Dec +46 27 37, dead on the star in question, so the identification is certain. (For a discussion of the double listing, and of Pickering's ingenious way of detecting "stellar" planetaries, see NGC 6766.)
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; but a search of the database for that designation returns no result, so the designation is shown in quotes.
Physical Information: As for many of the "stellar" planetaries discovered by Pickering and Copeland, NGC 6884 is hardly discernible from an ordinary star save with the use of filters. A "blink" comparison, in which a filter which blocks out light not given off by clouds of interstellar gas, is the easiest way for an amateur observer to tell which of the numerous stars in the region is the planetary nebula. When using such a filter (an OIII filter is the one most commonly used) stars appear noticeably fainter, while nebulous objects are nearly as bright as without the filter; so switching back and forth, the observer looks for objects which "blink" brighter than their neighbors when using the filter. However, as shown in the images below, NGC 6884 does exhibit a nebular ring around the central star. The ring is so much fainter than the star that it would not be visible either visually or in photographs taken with most amateur telescopes. The "normal" planetary nebula (such as imaged by the HST in the last image below) is part of the stellar object at the center of the ring, and I have yet to find any reference to the ring in the literature. This does not mean that it does not exist, and is merely an "artifact"; it is probably a roughly spherical cloud of material ejected by the central star a few thousand years ago, now faded to insignificance. If so, it represents the eventual fate of all planetary nebulae -- to become so large, rarefied, and poorly illuminated that they fade and disappear even as they continue to expand into interstellar space. The distance of objects such as NGC 6884 is typically more a matter of guesswork than direct observation, as the stars at their center are not Main Sequence stars, and have no "standard candle" to help us determine how bright they really are, and from that how far away they might be. In this case, studies of the expansion of the nebula (using HST images) by Palen et al yield distance estimates of 4 to 8 thousand light-years; not a terribly precise value, but still better than nothing. Given that and the approximately 1.2 arcmin size of the outer ring, the outer structure is about 2 light-years across, while the few arcsec apparent size of the "stellar" planetary corresponds to about a tenth of that value.

Historical Identification: Per Dreyer, NGC 6885 (= GC 4559 = JH 2071 = WH VIII 20, 1860 RA 20 06 07, NPD 63 55.7) is "a cluster, very bright, very large, rich, a little compressed, stars from 6th to 11th magnitude".
Physical Information: Given the duplicate entry, see NGC 6882 for anything else.

Historical Identification: Per Dreyer, NGC 6886 (Copeland, 1860 RA 20 06 29, NPD 70 25.7) is "a planetary nebula, stellar, equivalent to 10th magnitude". The position precesses to RA 20 12 42.5, Dec +19 59 22, dead on the star in question, so the identification is certain.
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Like most of Copeland's stellar planetaries, NGC 6886 is essentially indistinguishable from an ordinary star using ordinary methods of observation (its apparent size of 0.17 arcmin = only 10 arcsec); but see NGC 6884 for a discussion of the "blink" method used by amateur observers to identify such objects, or NGC 6766 for a discussion of the spectroscopic method used by observers of the late 1800's and early 1900's.

Historical Identification: Per Dreyer, NGC 6887 (= GC 4560 = JH 3822, 1860 RA 20 06 38, NPD 143 12.5) is "pretty faint, considerably large, pretty much extended, gradually a little brighter middle".
Physical Information: Apparent size 3.2 by 1.3? arcmin

Historical Identification: Per Dreyer, NGC 6888 (= GC 4561 = WH IV 72, 1860 RA 20 07 22, NPD 52 01.5) is "faint, very large, very much extended, double star attached". The second IC lists a corrected 1860 RA (per Bigourdan) of 20 07 01.
Discovery Notes: Bigourdan also observed the region on Jun 30, 1884, and stated that the region was "rich in stars", but that he could find no sign of the nebula; it was only on the date shown above that he found the nebula "20 seconds of time preceding" the NGC position (whence the correction in the IC2).
Physical Information: The Crescent Nebula is an emission nebula caused by the collision of two waves of gaseous emissions by the "bright" (7th-magnitude) star near its center, WR 136. The star is an approximately 4.5 million year old Wolf-Rayet star of perhaps 40 to 80 solar masses. Wolf-Rayet stars are very massive, extremely hot stars (originally O-type Main Sequence stars) which are near the end of their lives. A few hundred thousand years ago the star swelled up to become a red super-giant, and ejected a few tenths of a solar mass of gas at about 20 thousand miles per hour. About 200 thousand years later, it heated up to several hundred thousand degrees, and began ejecting about a solar mass of super-heated gas per ten thousand years, at nearly 1% the speed of light (3 to 4 million miles per hour). As the faster moving, hotter gas reached the shower-moving, cooler gas previously released, it created a supersonic shock wave, causing the nebula to emit visible (primarily red H‘) light, as well as ultraviolet and X-radiation. The complex filamentary structure of the nebula is real, but its spherical structure is tissue-thin in comparison to its size. Only the surface of the structure is glowing; the hot gas streaming away from the star is essentially invisible. Within a few thousand years the current nebula will fade away, as its gas disperses into the surrounding space; but within a hundred thousand years, a new and even more spectacular nebula will form when the star supernovas. WR 136 and its nebula are about 4700 light-years away. Given that and the approximately 18 by 12 arcmin apparent size of the nebula, NGC 6888 is about 25 light-years across.

Below, a HST false-color image of a shock-heated portion of the nebula. The black and white visible-light image shows the region covered by the HST closeup. (Image Credit NASA, Brian D. Moore, Jeff Hester, Paul Scowen (Arizona State University), Reginald Dufour (Rice University))

Below, a Chandra space telescope X-ray image of a region which includes the HST image above, superimposed on a ground-based image of the whole nebula. The X-radiation detected by Chandra (shown in false-color blue) represents gas shock-heated to about 2 million Fahrenheit degrees. (Image Credits: X-ray: NASA/UIUC/Y. Chu & R. Gruendl et al. Optical: SDSU/MLO/Y. Chu et al.)

Historical Identification: Per Dreyer, NGC 6889 (= GC 4562 = JH 3823, 1860 RA 20 08 06, NPD 144 23.0) is "very faint, large, a little extended".
Physical Information: Apparent size 0.9 by 0.7? arcmin

Historical Identification: Per Dreyer, NGC 6890 (= GC 4563 = JH 3824, 1860 RA 20 08 30, NPD 135 13.9) is "pretty faint, small, round, very gradually a little brighter middle".
Physical Information: Apparent size 1.6 by 1.3? arcmin

Historical Identification: Per Dreyer, NGC 6891 (Copeland, 1860 RA 20 08 32, NPD 77 41.2) is "a planetary nebula, stellar, equivalent to 9.5 magnitude". The position precesses to RA 20 15 07.4, Dec +12 44 15, about 2 arcmin north northwest of the star in question, but there is nothing else nearby which in any way matches the description, so the identification is certain.
PGC Designation Note: For purposes of completeness, LEDA assigned a PGC designation to this object, even though it isn't a galaxy; however, a search of the database for that designation returns no result, so it is shown in quotes.
Physical Information: Like many of Copeland's "stellar" planetary nebulae, the central portion of NGC 6891 looks very much like a star (its 0.35 arcmin apparent size corresponding to only 21 arcsec), but there is a faint outer ring visible in long-exposure photographs, which (as in the case of NGC 6884) was presumably ejected by the central star several thousand years ago, and is now fading from view; and even the inner region displays a complex structure in high-resolution images, such as the HST image below. The distance of planetary nebulae is typically more a matter of guesswork than direct observation, as the stars at their center are not Main Sequence stars, and provide no "standard candle" to help us determine how bright they really are. In the case of NGC 6891, the distance has been estimated from studies of the expansion of the nebula, as measured with HST images spaced over a period of about four years. The expansion rate for NGC 6891 turned out to be so slow that it could not be measured in the brief time involved; but comparison with the other objects studied suggests that it is at least 3000 light-years away, as any closer distance would have yielded measurable results (closer distances making the nebula and its expansion rate appear larger).