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Blinking Planetary

NGC 6826, HD 186924, PK 083+12 1, PN VV' 514, PN VV 242, PN G083.5+12.7, Caldwell 15, Blinking Planetary, IV 73, h 2050, GC 4514

RA: 19h 44m 48.15s
Dec: +50° 31′ 30.26″

Con: Cygnus
Ch: MSA:1109, U2:55, SA:8

Ref: SIMBAD

(reference key)

Type: planetary nebula

Mag: B=10.21, V=10.07

Size: ?
PA: ?

Historical observations

William Herschel (c.1784)

Synonyms: H IV-073

Discovered in 1793 by William Herschel with an 18.7-inch f/13 speculum telescope. He called it "a bright point, a little extended, like two points close to one another; as bright as a star of the 8-9 magnitude, surrounded by a very bright milky nebulosity suddenly terminated, having the appearance of a planetary nebula with a lucid centre; the border however is not very well defined. It is perfectly round, and I suppose about ahlf a minute in diameter. It is of a middle species, between the planetary nebulae and nebulous stars, and is a beautiful phenomenon."

Burnham, S.W. (1894)

Burnham, S. W. () "Measures of planetary nebulae with the 36-inch equatorial of the Lick Observatory", Pub. Lick Obs., vol 2, p159-167. This beautiful object is almost an exact duplicate of the p[lanetary nebula in Draco. It is slightly elliptical with the longer axis in the direction of 295. ... longer diameter 26.6'' and for the shorter 24.3''. There are a number of stars nearer than the one measured. The nearest, about 14m is 27'' from the central star, in the direction of 283.1.

Published comments

Terzian, Y. (1980)

Terzian Y (1980) Q.J. R.astr.Soc vol 21, p82-92 [09.16.1] notes that the nebula has a faint outer giant halo.

Sulentic & Tifft (1973)

The RNGC (Sulentic and Tifft 1973) notes that this is a 9.0 mag planetary nebula.

Photo index

Photo Index by Jim Lucyk: Sky&Tel. 9/80 p257, Deep Sky #12 Fa85 p14, Deep Sky #6 Sp84 p7, Deep Sky #20 Fa87 p12.

Doig, P. (1925)

Doig, P. (1925) Notes on the nebulae and clusters in Webb's 'Celestial Objects for Common Telescopes' (Sixth edition, Vol.ii). Part I. M.N.R.A.S., 35(5), 159.

Modern observations

Walter Scott Houston

Houston writes: "With a total light equal to a star of magnitude 8.8, in modest apertures this planetary shows a fine greenish disk about 25 arcseconds across ... since the planetary's 11th mag central star was easily seen by Willaim Herschel and his son John, they considered this nebula a transition object between regular planetaries (whose central stars were too faint to be seen) and stars involved in diffuse nebulae. At 300x, a 10-inch reflector I had in Kansas showed NGC 6826 to have uniform light across its centre. The planetary takes magnification well, and is a fine object for even small apertures."

Mullaney, J

Mullaney writes: "Some 27 arcseconds by 24 arcseconds in size, it shines at 9th magnitude and has an obvious 11th mag central star. In the early 1960's Wallace McCall and I came up with the nickname because of the planetary's unusual behaviourin the eyepiece - direct vision shows only the central star and a little trace of the nebula itself, while averted vision drowns out the central star with bright blue nebulosity. Alternating back and forth between direct and averted viewing produces an incredible blinking effect. Here's one of the few deep-sky objcts that does something in the eyepiece! The effect can be glimpsed in telescopes as small as a 3-inch refractor at 75x, but it becomes ever more striking as aperture increases. (Some other planetaries exhibit this unusual behaviour, but none to the extent of this one.)"

Bushnall, Darren (1993)

Darren Bushnall (Hartlepool, Cleveland) observing with a 8.5-inch f/6, writes in the The Webb Society Nebulae and Clusters Section Report No. 11, January 1993: "Easily seen at low power as a small fuzzy star, about 1.5' from a mag 8 star on its S.p. side. At x272 the middle was bright and condensed, about 15 arcseconds diameter; the outer edge of the nebula fades suddenly and was about half the brightness of the central region. Central star very bright."

Watson, Brent (1995)

From: BRENT WATSON(bjwatson@IOMEGA.COM) Date: Wed, 25 Oct 1995 16:34:45 -0600

Subject: NGC 6826 observation

The first time I ever saw the Blinking Planetary (NGC 6826) was fifteen years ago with a group of friends on Bald mountain in eastern Utah. The elevation there is about 10,500 feet and we had gone there for a dark of the moon weekend. I had my new 22 inch scope, there were a couple of 17"and 13" Coulters, and the usual smattering of SCTs and smaller reflectors. We even had a 9" Clark refractor there.

One of the folks there suggested I look at 6826 with the 22 inch. I looked it up and pointed the scope at it and was astonished at its blinking nature. Not knowing the mechanism for the blinking phenomenon at the time, I wondered if others could see the same "blinks" as I did. Several other people pointed their scopes at 6826. We then spent the next half hour yelling out "It's on" and "It's off". The conclusion was that everyone saw the same "blinks" simultaneously!

Of course, now I am left to postulate that the power of suggestion had more to do with the simultaneous observations than actual light output from the nebula, since the light output is constant. No, there was no alcohol nor altitude sickness involved.

Anyway, just one of those lighter, more memorable observing experiences. I still cannot even think of NGC 6826 without thinking of that experience.

Brent

Tom Lorenzin

Tom Lorenzin, in the e-version of "1000+ The Amateur Astronomers' Field Guide to Deep Sky Observing", notes: "8.8M; 25" diameter; 11M center star; looking directly at central star (with <6-in. aperture) makes nebula wink out due to foveal insensitivity."

Hogsten, Scott (IAAC)

Observer: Scott Hogsten; Your skills: Intermediate (some years); Date/time of observation: 7/28/98 - 10:40; Location of site: Perkins Obs. Delaware Ohio (Lat , Elev ); Site classification: Suburban; Sky darkness: 5 1-10 Scale (10 best); Seeing: 6 1-10 Seeing Scale (10 best); Moon presence: Minor - crescent or far from object; Instrument: 12.5" f5 Dob; Magnification: 75x 90x 150x; Filter(s): None

Description: "Blinking Planentary" Bright Round planetary that does not "blink" for this observer. I could easily hold this object steady in the center of the eyepiece without using averted vision. At 75 x it is easy to overlook this planetary in unsteady skies, stepping the power up to 90x definitely reveals a small disk, at 150x this planetary is a small blushish ball that is not quite uniform in appearance. This planetary gives an impression of being more 3D than other planetaries.

Gramer, Lew (IAAC)

BTW, on that "Blinking Planetary" in Cygnus - next time you get a peak at it, look for a fairly bright central star. With the right magnification, that central star will seem to "blink" in and out of visibility: you'll see it easily with averted vision. But then if you switch to looking straight at it, it'll seem to disappear - a pretty neat effect!

By the way, what other planetaries have folks seen this effect with?

Clear skies, and keep those great logs coming from Buckeye country!

Lew Gramer

Maloney, Patrick (IAAC)

Observer: Patrick Maloney; Your skills: Advanced (many years); Date/time of observation: 28/Jul/1998 0535UT; Location of site: Rocky Mtn Natl Park, Colorado (Lat , Elev 8400ft); Site classification: Rural; Sky darkness: 6.0 Limiting magnitude; Seeing: 8 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 10" Starsplitter Newtonian; Magnification: x218; Filter(s): ; Object(s): NGC 6826 - Blinking Planetary; Category: Planetary nebula.; Class: IIIa; Constellation: Cyg; Data: mag 8.8 size ; Position: RA : DEC :

Description: Very bright. Three distinct areas visible. The centre is almost starlike and extremely bright. This is surrounded by a very bright, smooth, almost circular area. Outside this is a dimmer area, which nearly doubles the apparent width of the object and gives it a clear elongation.

Observer: Patrick Maloney; Your skills: Intermediate; Date/time of observation: 31 Aug 1980; Location of site: Unknown; Site classification: Suburban; Sky darkness: 5.5 Limiting magnitude; Seeing: Unknown; Moon presence: None - moon not in sky; Instrument: 4.5" reflector; Magnification: 45x, 150x; Filter(s): none; Object(s): NGC 6826 (Blinking Planetary); Category: Planetary nebula.; Class: 3a+2; Constellation: Cyg; Data: mag 9.8 10.44m ctrl star, size 27"x24"; Position: RA: 19:44:48.17 Dec: +50:31:30.4;

Description: High power reveals a bright stellar nucleus surrounded by a bright nebular disc. In the direction WNW-ESE, the nebula is elongated to an oval shape. The outer nebulosity is fainter than the nuclear disc but is easily visible to direct vision. [The drawing accompanying this description shows the direction of the suspected elongation in the same orientation as that drawn in a later 1984 observation (and the same as seen in July 1998 - see log posted earlier).]

Coe, Steve (IAAC)

Observer: Steve Coe; Your skills: Advanced (many years); Date/time of observation: Aug 97; Location of site: Strawberry, Arizona USA (Lat +34, Elev 7000 ft); Site classification: Rural; Sky darkness: 8 1-10 Scale (10 best); Seeing: 6 1-10 Seeing Scale (10 best); Moon presence: None - moon not in sky; Instrument: 13" f/5.6 Newtonian on Bigfoot German EQ ; Magnification: 100X, 160X, 220X; Filter(s): none; Object(s): NGC 6826

NGC 6826 is the Blinking Planetary. This medium sized, 9th magnitude planetary can be located at 100X. It appears as a non-stellar blob in the Milky Way. I first saw the blinking effect in an 8" scope at 200X. If you look directly at the planetary the central star is prominent compared to the greenish nebulosity. Then averted vision will make the nebula appear brighter and overwhelm the star. Alternating between direct and averted vision will produce a blinking on-then-off effect that is fascinating. In the 17.5" the effect is unmistakable. There are several other planetary nebulae that have the right central star to nebula brightness to show off this effect.

Using 13" f/5.6 on a excellent night at 7000 ft. in Arizona, this planetary is bright, large, somewhat elongated and greenish. The central star is easy at 150X as it floats in a rich Milky Way field of view. On a 7/10 night, it is bright, pretty large, very little elongated 1.2 X 1 in PA 170 at 100X. It is easily found at 100X. The central star is better seen at 220X, but the blinking effect is better at 100X, the central star "goes away" with averted vision. The PN is light green at all powers.

Ultimate Star Party, McDonald Obs. Oct. 95, S=6, T=8, 25 in. f/5-- NGC 6826 (blinking planetary) in 25" with 9mm; "large" central star is obvious. The dark markings can be seen in the bright disk, they are about 60 percent of the way out from the core and are thin dark lines. The blinking effect does not happen very well at this aperture. The large central star is a stellar wind effect, so we are not seeing the actual central star, but a bright annulus of gas surrounding it.

Williams, Harold (IAAC)

Observer: Harold Williams;Your skills: Intermediate (some years);Date/time of observation: ;Location of site: Philadelphia, PA (Lat 40N, Elev 100);Site classification: Urban;Sky darkness: Limiting magnitude;Seeing: 1-10 Seeing Scale (10 best);Moon presence: None - moon not in sky;Instrument: Meade LX10 8" SCT;Magnification: 50x,100x, 222x;Filter(s): none

Description: This is the Blinking Planetary Nebula. I didn't really expect to find this object since the humidity was causing the lights of Philadelphia to be scattered quite high above the horixon. But, I quickly found it in the 40mm eyepiece at 50x. It was barely indistinguishable from nearby stars but something didn't look the same. Also, the digital setting circles told me I was on the right spot. Going to 100x told me it definitely wasn't a star. But, I was still not sure this wasn't the object I was looking for because it remained a round, fuzzy spot even as I looked right at it. But, after a few moments, it suddenly became a distinct point of light as if it were a star. Then, when I would blink, it would return to being the round, fuzzy spot. I became obsorbed in this phenomena and spent maybe 10 minutes staring and blinking. This was easily my favorite object of the evening.

McNeil, Jay [amastro]

Hi all, With the recent spell of decent transparency combined with rather excellent seeing here in SE Texas, I have been hammering away on a current project concerning the observation (and drawing) of microstructural details within nearby multiple-shell PNe. Such observations may include such odd features as FLIERs, outer haloes, and detailed shell structure within the nebula itself. I just got through transcribing my notes from the latest outing involving me and NGC 6826 (the Blinking). These notes are an accumulation of two back-to-back nights of observing with the spells of best seeing dedicated to studying just this object.

I spent a total of about 2.5 hours studying and drawing this object on two seperate nights. The seeing was subarcsecond along with quite good transparency on both occassions, and the most pleasent and revealing view came at 586x with Mira, my 16-incher. A power of 855x was also used at times to glimpse smaller, more intricate detail within the nebula.

The brightest part of the nebula itself formed a rather high surface brightness oval of nebulosity approximately 30"x25" and elongated East south-east/ West north-west centered nicely upon the bright 10.41 magnitude central star. This nebulosity was somewhat diffuse and displayed obvious mottling at its very edges, especially near the tips of its major axis. Within this bright, diffuse envelope, there was a second circumstellar shell of ~10" diameter that appeared to have a slightly more distinct and less diffuse appearance than the previous envelope. When the seeing steadied, this inner shell was very well-defined displaying rather sharp edges in contrast to the outer envelope. The inner shell did, however, seem very slightly elongated in the same direction as the larger outer feature, and the edges representing the minor axis were likewise slightly brighter than the very tips of the inner rim (as if there was evident limb-brightening along the minor axis of the nebula, throughout). The area internal to this inner ring and nearest the central star was apparently darker than any other part of the nebula, which suggested that the brightened inner shell was somewhat hollow. However, this hollowness was obviously not as dark as the background sky at even the highest of powers.

The next most obvious feature of the complex nebula was the south-eastern FLIER complex, which appeared as a very slightly (<3") non-stellar nebulous "knot" located at the very edge of the outer envelope's most eastern point. As the seeing fluctuated at such high powers, however, this peculiar feature became obviously stellar in appearance and seemingly got brighter as the light of its tiny disk appeared to become more concentrate rather than diffuse. With a Lumicon Deep Sky Filter applied at 586x, this stellaring became nearly as apparent as the nebula's filtered nucleus at times. No other filters of narrower bandwidth (OIII, H-beta, Ultrablock) were of much use in this particular situation, and only the Deep Sky seemed to gently improve the view of detail.

At nearly the opposite side of the nebula's outer envelope, there resided the north-western FLIER complex. Obviously much fainter and slightly more diffuse than it's eastern counterpart, this small feature very rarely appeared as a brighter stellaring. Even when filtered, it remained a quite diffuse knot.

Shell structure within the nebula seemed quite complex. At 855x, there appeared to be a very elongated internal disk that consisted of the previously mentioned inner shell along with very delicate extensions that protruded the entire outer envelope of the nebula and appeared to end with the FLIER complexes at their very tips. The view of this extremely delicate disk seemed somewhat reminiscent of a recent view of NGC 7009 (the Saturn) at such power, however, with the ansea being slightly more broadened to give the disk-like structure. Furthermore, there were times when the individual FLIER complexes obviously extended very slightly beyond the bright outer envelope of the nebula, which gave the entire nebula an "oddly" more elongated structure (as if the very edges of the major axis consisted of small "nipples").

At the most extreme use of adverted vision, there faintly appeared to be an ~35" low surface brightness roundish halo of nebulosity enveloping the nebula's entire structure (including the nipple-like extensions of the FLIER complexes). I am aware of NGC 6826 having a 138" post-AGB outer halo, however, I am almost certain of it's invisibility. This ~35" diffuse glow may, however, represent the innermost and brightest portion of this feature.

Hope this atleast gave y'all a break from the "nomenclature crap"--I know this one exists! Jay McNeil

Knisely, David [amastro]

Hi there (apologies to the group for the nomenclature crap). RE: NGC 6826. This is indeed a wonderful object at high power. In my ten, it looks good even when the moon is out. I observed it one night with a friend when the gibbous moon was out allowed some high power looks at it. It radically changes appearance from the simple "quick-look" descriptions in many books and articles (no more "small bluish-green disk that blinks"). At 310x, like Jay, I also saw a darker region around that blazingly-bright central star (if it gets any brighter, it might blow out the nebula :-)). I also noted a slightly broken annular shell with brighter segments on the north and south sides. With my 2.5x Powermate, I should go back out and get another look. Clear skies to you. David Knisely

Callender, John

Observer: John Callender

Instrument: 8-inch Dobsonian reflector Location: Carpinteria, CA, USA

Light pollution: light Transparency: good Seeing: fair

Time: Wed Jul 2 08:00:00 1997 UT Obs. no.: 181

Per Burnham's, a mag 8.8, 25"-diameter planetary. Was an easy fuzzy "star" at 49x. At 122x was a ghostly little circle, gray and uniform. At 244x I could see the central star with averted vision, and thought I detected a slight elongation in an east-west direction, and just possibly a hint of structure in the outer reaches.

Brian Skiff

PK: *(s) assoc on W edge of br core of neb (~1' diam). vf circ halo 2'+ diam.

POSS: m11 * 1'.55 SSW.

8cm - *ar @ 20x. BS, 26Aug1983, Anderson Mesa.

15cm - vbr & non*ar @ 50x. 80x shows blink effect of cen * while jumping btwn direct and averted vis. effect not as good at higher powers. cen * sl brtr than m11 * 2'.5 S. 195x shows poss wk annularity in very center, but contrast is low. BS, 29Sep1989, Anderson Mesa.

18cm - Pluto camera guidescope, 180x: brtr than M57. cen * rel easy, m12. neb nrly circ, almost uniform, about 15" diam. m11 * 35" SSW. BS, 26Aug1983, Anderson Mesa.

25cm - obvious @ 47x. circ w/diffuse edges. br *-like spot in center. 244x gives good view.

30cm - easy. elong pa120. cen * vis, a m13.-13.5 pinpoint. 25" diam, elong by 15%. occas uneven on W, w/dkr patch nr cen *, patch 8" across. S 2' is m12 *. in rich fld.

Paul Alsing

82-inch at McDonald - Observing Report

[amastro] posting, Sat Nov 25, 2006

82" telescope, McDonald Observatory near Fort Davis, Texas, USA

f/13.7, 35mm Televue Panoptic (5' fov, 812x)

Large blue-green, 2-stage oval, slightly elongated E-W. The central portion has slight ansae at the ends of the long axis and has stronger color. The fainter outer ring has a sharp outer edge.

Contemporary observations

Magda Streicher

(no date)

Alldays (22.50S, 20.12E, 770m).

12-inch f/10 SCT (95x, 218x)

NGC 6826 is a fine bright green-bluish planetary a little elongated east-southeast and west-northwest. The planetary displays a non-stellar blob in the Milky Way with a bright 10.6 Magnitude central star. This beautiful nebula certainly blinks as its name stated. To the eye it brightens up to a star-like point just to fade out again like a hazy patch of light. The nebula exhibits a soft disk with a hint of an outer envelope. William Herschel discovered this planetary in 1793.

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