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RA: 19h 44m 57.8s
Dec: −14° 48′ 11″
Ch: MSA:1339, U2:297, SA:16
Ref: SIMBAD, Corwin
Type: galaxy, IB(s)m
Mag: B=18, V=?
Size: 14.79′ x 13.18′
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NGC 6822 = IC 4895, which also see. The IC number is easily explained, but I am a bit puzzled at the record concerning NGC 6822 itself. William Sheehan, in his biography of Barnard "The Immortal Fire Within" has the galaxy being "swept up with the 5-inch Byrne refractor in 1884". However, in his short note on its discovery in Sidereal Messenger, Barnard says that he used the 6-inch refractor to determine its position, and that it is in the same low-power field (in the 6-inch) as the well-known planetary nebula, NGC 6814 [sic; NGC 6818]. Barnard is also a bit parsimonious with his description of the galaxy, calling it only "exceedingly faint". There is nothing about its size or shape, so the NGC description "vF, L, E, dif" probably reached Dreyer in a letter.
This galaxy is important historically as it is the subject of Edwin Hubble's first published paper on Cepheids in external galaxies. Though he announced the discovery of extragalactic Cepheids in M31 in 1924, he chose NGC 6822, "a remote stellar system", as the first to have his systematic studies reported in the Astrophysical Journal (Volume 62, page 409, 1925). M33 and M31 followed in 1926 and 1929, respectively.
Extragalactic astronomy begins here, too.
A member of the Local Group, this galaxy, also known as Barnard's Galaxy, lies in eastern Sagittarius.
The maximum dimensions are about 20' by 11' but the brightest portion is an elongated central core or bar measuring about 8' by 3' and oriented almost due north-south. With large telescopes it is well resolved into an irregular mass of hundreds of thousands of stars, gathered here and there into irregular clumps and clusters; the brightest individual stars being about 15th magnitude. Van den Bergh (1975) gives the total integrated photographic magnitude as 9.2; the object is difficult visually because of its large area and therefore low surface brightness.
As with other large, low surface-brightness objects, the key to success is a wide field, and not aperture.
See "New Nebula near General Catalogue No. 4510" for Barnard's discovery announcement.
The NGC description reads: "Very faint, large, extended and diffuse"
Edwin Hubble reported that the galaxy was easy with a lowpower eyepiece in the short focus 4-inch finder of the 100-inch telescope at Mount Wilson Observatory, but that it was "barely discernible" in the main instrument.
W.T. Olcott in 1929 referred to it as "one of the most remarkable objects in the heavens" but called it "a marvelous star cluster."
Burnham has found "the galaxy not particularly difficult on 6 to 10-inch telescopes with wide-angle oculars; it is actually somewhat easier to detect than the Veil Nebula in Cygnus."
pF, 20'x4' group and stars and small faint nebula involved in diffuse nebulosity.
The RNGC (Sulentic and Tifft 1973) notes that this is a 10.0 mag galaxy. Their coded description reads IRR,RESOLVED,LOCGRP.
Schmidt K.-H., Priebe A. & Boller T. (1993) Nearby galaxies. Revised machine-readable version of the catalogue. Astron. Nachr., 314, 371. [1993AN....314..371S]
Other names: "D209,I4895". Inclination: (face-on, in degrees) 53 Total photoelectric blue mag 9.31 Logarithm of the angular diameter D25 (arcminutes) 2.19 Blue photographic magnitude 10.3 This galaxy is included in a sample of galaxies with velocity less than 500km/s with respect to the centroid of the Local Group. [Nearby Galaxies. Schmidt K.-H., Priebe A., Boller T. (Astron. Nachr. 314, 371 (1993))]
NGC 6822 Barnard's Galaxy, Sky&Tel. 8/67 p120.
Note on the distance of NGC 6822. Harv Coll. Obs. Bulletin 796. [192?BHarO.796a....S]
de Vaucouleurs, G. (1975) Nearby groups of galaxies. In: Kuiper, G. (ed) Stars and Stellar Systems. Volume 9: Galaxies and the Universe. Chapter 14, p557.
p 589: Listed in Table 9: "DDO dwarfs > 8 arcmin"
DDO 209 = NGC 6822, apparent diameter = 12.5 arcmin.
Hartung notes that "this large, faint object needs a clear dark night for observation. It is an elliptical haze about 8' by 4' in PA 20 , rising only very broadly towards the centre and including some faint stars which no doubt belong to the field. It may be seen plainly but faintly with an 8-inch."
Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "11M; 20' x 10' extent; nearby dwarf galaxy; much extended and faint; easiest with <50x and wide field; !good supernova prospect! planetary N6818 45' to NNW."
NGC 6822 Donald J. Ware:" Barnard's Galaxy. Only a short distance away from NGC 6818, this elusive galaxy is actually a member of the Local Group of galaxies. It is a low mass galaxy whose feeble light is spread over an area of about 15'x5', and is extended in the north-south direction. This faint object is best seen on nights of excellent clarity, and with instruments of moderate aperture."
From: email@example.com (Thomas J. Kunsitis)
Subject: Re: Binocular Observations -NGC 6822
Date: Fri, 30 Aug 1996 14:06:22 GMT
I have seen it with my 13" telescope. I saw it on a good night (for Richmond, Virginia) with a limiting magnitude around 6.0. According to my notes it appeared large and faint with low surface brightness and ill defined edges. It was not an easy object for the 13" scope. I did not even try to see it in the finder or with binoculars. Tom Kunsitis - Richmond, Virginia USA
Subject: [amastro] Dwarfs in a dwarf telescope
I spent a bit more time last night (5 Sep UT) casting about with the Pronto at Anderson Mesa on another excellent post-monsoonal night. Among the targets were some low-surface-brightness Local Group dwarf galaxies: in decreasing order of brightness NGC 6822, IC 1613, and the Wolf-Lundmark-Melotte galaxy. At about mag. 9 and mean surface brightness about mag. 14.5/square arcmin, NGC 6822 was readily spotted at 30x. IC 1613, a magnitude fainter, was a marginal object, and WLM, somewhat fainter still by the specs, was apparently a bit too faint and I couldn't reliably see it. I'd like to try WLM again perhaps from a more southerly location.
In the field with NGC 6822 is the bright planetary NGC 6818. Since this was substellar at 30x, I estimated its brightness (without filters) with respect to the mag. 8 star west (HD 186107) as about 0.6 mag. fainter. This star has V=8.1, but is quite red, B-V=1.7, so assuming the 0.2(B-V) factor to get visual magnitudes, the planetary comes out right at mv=9.0, perhaps slightly brighter than Marling's mv=9.3. One might also make an estimate wrt the fainter star east (HD 186368, V=9.5/B-V=0.3), since its color is more neutral.
I also looked at NGC 6760 in Aquila. This was comfortably faint for the Pronto. The halo reaches roughly to a relatively bright star on the NE side of this cluster. This is mentioned by Luginbuhl & Skiff as mag. 10.5, but is actually mag. 12 or 12.5 (Kepple & Sanner also wrong.) This star was used by several 19th century observers (Winnecke, Lord Rosse, Bigourdan) as an astrometric reference; Bigourdan also calls it mag. 12 or 12.2 in two of his four observations.
While poking around near NGC 6760, I came across what appeared to be a large "absorption hole" starcloud and a tiny fuzzy knot half a degree north of it. After refinding it from 6760 with atlas in hand, I was surprised to learn that these were NGC 6755 (starcloud) and NGC 6756 (knot). NGC 6755, although a nice object at 30x, has what is to me a distinctly non-open-cluster appearance (luminosity function not right)---I'd be willing to bet this is nothing more than a starcloud. NGC 6756 was inscrutable, simply too small and faint for the Pronto at 60x.
Coe, observing with a 13" f/5.6, notes: "Very faint, very large, elongated 2 X 1 in PA 0, not brighter in the middle at 60X. With averted vision this low surface brightness galaxy was very mottled. This object was more obvious in the 11X80 finder than it was in the 13" with a 2" eyepiece."
Your skills: Intermediate; Date and UT of Observation: 1997-07-5/6, 04:00 UT; Location: Savoy, MA, USA (42N, elev 700m); Site classification: rural; Limiting magnitude: 7.3 (zenith) 6.8 (near object); Seeing: 3 of 10 - pretty good; Moon up: no; Instrument: 4" f/5.4 Genesis SDF refractor; Magnification: 15x, 20x; Filters used: None; Object: ngc 6822 (Barnard's Galaxy); Category: Dwarf Galaxy [IB(s)m IV-V]; Constellation: Sgr; Data: mag 9.31? size 15'x13'; RA/DE: 19h45m -14o48m
Description: This famously elusive Local Group galaxy was invisible in a 35mm Panoptic (15x). I used detailed charts to pinpoint the spot, and tried every seeing trick I know: nothing. However, not giving up hope (and knowing that a Genesis under dark skies gave the best chance I would have for a while to spot this wiley animal), we went on to try a 27mm Panoptic (20x). Barnard's faint haze-patch suddenly popped into view! It was clearly apparent with averted vision, NNE of a distinct triangle of Mag. 5-6 stars (including 55 and 54 Sgr), and NNW of a smaller, similarly-shaped triangle of Mag. 9 stars. It appeared (to both our eyes independently) as an extremely faint, elongated smear running roughly NE-SW, about 15' long and perhaps 7' at it's widest. Mottling was apparent to my eyes near the N edge, and also near center. A subtle "elbow" shape could be perceived with careful concentration, bending W. The galaxy became somewhat brighter toward the center of this elbow, with the highly irregular, nebulous "core" standing out occasionally to DIRECT vision, showing apparent elongation E-W. Some stellarings could be seen throughout, but at this power it would have been difficult to distinguish HII regions from stars. What a THRILL to see this mysterious object again after 15 yrs!
Hi, Scott - this is the famous "Barnard's Galaxy," and your description ; is quite apt for the low power view - it is sometimes little more than a ; faint "stain" on the sky; next chance you have, though, go out and try ; this one at high magnifications (the 150x you describe is a good start), ; or put a UHC or Ultrablock filter on your scope and have a peek. Under ; the nice dark skies you describe, your 12" scope should show you a few ; things that you didn't quite pick up the first time, like, possibly ; individual bright stars (!) and brighter H-II regions. The SEDS NGC ; browser site has a good picture of it, and there are some good observing ; websites for this object (notably, ; http://www.angelfire.com/id/jsredshift/ - Jim Shields's site.;
Nice reports - have fun! Bruce Jensen
Your skills: Intermediate (some years); Date/time of observation: Aug 19,1998 11:45 EDT; Location of site: McConnelsville, Ohio (Lat 39N, Elev ); Site classification: Rural; Sky darkness: 6.5 Limiting magnitude; Seeing: 8 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 12.5" f5 Dob; Magnification: 125x, 150x; Filter(s): ; Object(s): NGC 6822; Category: External galaxy.; Class: ; Constellation: SGR; Data: mag 8.8 size 20"x10"; Position: RA 19:44.9 DEC -14:45;
Description: Very difficult galaxy. This galaxy would be in the same field as the Planetary Nebula NGC 6818 using a low power wide field eye piece. The surface brightness if this galaxy is very low and it is very easy to hop right past it. The galaxy itself appeared as a very faint brightening of the background. I could not detect any structure what so ever even though the galaxy is quiet large
Thanks for the interesting comments about Barnard's Galaxy, Bruce! I have never taken the time to explore the constituent objects within n6822 myself - sounds like a great project. And thanks for the link to Jim Shields' *EXCELLENT* deep-sky Web pages! I'll be exploring them for a while too. :)
BTW, the general rule of thumb (now almost cliche) among deep-sky observers, of using higher magnification to increase contrast, may not be TOTALLY appropriate for certain objects like this one... I note in a previous log that the optimum magnification for perceiving this large, low-surface-brightness object AS A WHOLE, was extremely low.
In fact, using higher powers (and thus a narrower annulus of sky around the object) actually made it impossible to see! Of course, the HII regions, bar, OB associations, and other gross features (including resolved stars) will only be accessible at much higher powers. But to perceive this object in its full beauty - as E. E. Barnard originally did - do not be too overcome by the current craze to view everything at 200x or above. Instead, try a variety of filters, magnifications, and *apertures* (including binoculars!) to see what YOU perceive as the best view...
Well anyway, here's an observing log I posted to IAAC last year:
Note the mention of brighter direct-vision details - good targets for detailed viewing with much higher magnifications and larger apertures. Also keep in mind what I neglected to mention - that attempts to see the same view with a higher power eyepiece (12mm Nagler, 45x) failed...
What are the experiences of some of our deep sky mavens on the list, with this grand-daddy of the Low Surface Brightness galaxies?
Observer: Bruce Jensen; Your skills: Intermediate (some years); Date/time of observation: 8/22/1998, approx. 0500 UT; Location of site: San Antonio Valley, CA (Lat approx. 38 degrees N., Elev 2,000 ft.); Site classification: Rural; Sky darkness: 8 of 10 1-10 Scale (10 best); Seeing: 8 of 10 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 18" F/4.5 dob-newt; Magnification: 92x, 145x, 225x; Filter(s): Ultrablock; Object(s): NGC 6822, Barnard's Galaxy; Category: Extragalactic star.; Class: Dwarf Galaxy, irregular w/ apparent bar; Constellation: Sag; Data: mag 8.8 size 15' x 18'; Position: RA 19:44.9 DEC -14:48;
Description: Barnard's Galaxy lies about 10 degrees northeast of the handle of the Sagittarius teapot. It is a faint dwarf galaxy that accompanies the Milky Way on it's journey as part of the local group, and is close enough for easy resolution of physical features such as bright stars and nebulae. At 92x, it showed very faintly but unmistakeably as a large hazy patch with some elongation to it, about twice as long as wide. Closer inspection revealed a few areas of haze with more substance to them, likely H-II regions. Use of 145x and 225x revealed fine-grained mottling of the haze, with a few bright points of light poking out distinctively. I am not familiar enough with the object to know if any of these were stars of that nearby galaxy or not, but the mottling showed that it was indeed more than just a nebula. Back to 92x, the Ultrablock filter improved contrast on the whole galaxy; more importantly, it brought out a number of nebulous H-II regions that were nearly invisible without filtration. Although there are several of these regions, three were fairly easy when filtered at 145x, with a few more faintly suspected. At 225x they were more obvious even without a filter, and two dimmer ones became easier. No individual OB associations of stars were identified. This is a most fascinating object, worth turning any scope to. --
1995 May 26, 03:00. 11x80 binoculars. Exact spot studied, limiting magnitude 9.5. Nothing seen.
1995-06-01: 11x80. Kelsey Farm. 23:00 SAST. This is confusing me know. I imagine I see something long and narrow in this region, extending further than the U2000 symbol, using averted vision.. This is most, most uncertain.
1997 July 6, Sunday, 21:00 - 23:00 Jonkershoek. 11x80's tripod-mounted. Well studied. Nothing seen.
1997 July 7, Monday, 21:00 - 24:00 Jonkershoek. 11x80's tripod-mounted. Not found.
Observing site: Pinnacles overlook
[19h 45m 0s, -14° 48' 0"] A huge, low contrast smudge. No bright middle.
The Messier objects
The Bennett objects
The Caldwell list
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