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Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

For those in northern latitudes similar to the southern part of the UK, and northern mainland Europe, August brings a welcome return of darkness - though those further north in latitudes similar to Scotland and Scandinavia will have to wait until the mid part of August to enjoy it.  Permanent Astronomical Twilight will continue for those in latitudes around the Shetland Isles and further north until the tail end of August, but for the rest of us, true darkness can be enjoyed throughout the month.  For those readers in the southern hemisphere, Midwinter is now past and the nights are beginning to get shorter.  But wherever you find yourself in the world, as ever, there's plenty to see.

 The Solar System


The Moon


The Moon starts August on the Aquarius/Pisces borders, at a few days past Full - rising a little before 11pm BST in the evening on the 1st. Being relatively close to the preceding Full Moon, this is not the optimum time for deep sky observations, or imaging faint objects without significantly narrowband filtration.


The Moon reaches Last Quarter on the 4th, while residing in The non-zodiacal constellation of Cetus.


The Moon reaches New as it joins the Sun on the Leo/Cancer borders on the 11th, after which it becomes an evening target. On the evening of the 14th, it may be possible to observe the very slim New Crescent Moon, sitting alongside Venus, in Virgo, just after sundown, with the two bodies separated by about 5 degrees (when viewed from Europe). 


The Moon and Venus, sunset, 14th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


The Moon reaches First Quarter in Virgo on the 18th, on the Scorpius/Libra borders. Three days later, the Moon passes close to Saturn, sitting to the north east of the ringed planet by about 5 degrees. 


The Moon becomes Full on the 26th, in Aquarius. Again, as was the case in early August, this is not the ideal time for deep sky observations and imaging. 


The Moon ends the month at Waxing Gibbous phase on the Cetus/Aries borders. 





At the beginning of August, the innermost planet is a faint +3 mag, showing a 11 arc second diameter, 7% illuminated disk. Mercury at this point, while separated from the Sun by 13 degrees, now sits lower in the sky than the Sun (from the temperate northern hemisphere), making it unobservable. 


Mercury reaches inferior conjunction (in between the Earth and the Sun) on August 9th, when it passes our parent star 5 degrees to the south in Cancer. After which it will emerge into the morning sky, though will remain unobservable for a little while until the angular distance between the two increases and Mercury's phase becomes larger. 


Mercury reaches greatest western elongation on the 26th - by which point circumstances for observation have improved dramatically. The planet is now +0.0 mag, presenting a 40% illuminated, 7.5 arc second diameter disk - which stands 15 1/2 degrees high in the east at sunrise (from latitude 51 degrees N). 


By the end of the month, Mercury is -0.6 mag and is 6.7 arc seconds across, showing a 57% phase. It stands 14 1/2 degrees high in the dawn sky at sunrise (again, from latitude 51 degrees N).


 Mercury at sunrise, 31st August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,



In early August, Venus is found on the Virgo/Leo borders at a brightness of -4.2 mag. Presenting a 20.6 arc second, 56.6% illuminated disk, the planet stands just under 13 degrees high in the west at sunset (from latitude 51 degrees N). 


Mid-month is significant as far as Venus is concerned, as the planet reaches greatest eastern elongation from the Sun in the 17th. But this point Venus sits at close to (though not exactly), a 90 degree angle from the Sun from our perspective. On the 17th, Venus presents a 48.7% illuminated, 24.4 arc second diameter disk, shining at -4.2 mag.  Venus stands just under 10 degrees high at sunset on the 17th (from latitude 51 degrees N).  When viewed from the equator, on this particular day, Venus stands significantly higher in the sky at sunset, as the planet's separation from the Sun is now 45 1/2 degrees. From this point in time, the figure will decrease as Venus continues on its inner orbit towards us. It will continue to grow bigger and brighter, but foreshortening of illumination will also continue to decrease its phase. 


Venus at greatest eastern elongation, sunset, 17th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

By the month's end, Venus is found 1 1/3 degrees south of Spica, Alpha Virginis, shining at an impressive -4.4 mag. Sadly for observers in the temperate northern hemisphere, it will appear low in the sky at sunset - standing just under 7 1/2 degrees high (from latitude 51 degrees N). The planet displays a 29.1 arc second, 40.5% illuminated disk at this point in time. 





Following late July's Martian opposition, Mars is just past its peak of brightness and size, but presents a fantastic and practically unmissable opportunity for observation no matter where in world you find yourself. Being in the southwestern reaches of Capricornus, Mars will appear better in the eyepiece the further south you are on Earth. The Red Planet stands 12 3/4 degrees high in the south at transit point (from 51 degrees N) on the 1st, shining at a striking -2.8 mag, showing a 24.3 arc second diameter disk. 


Mars at transit point, 1st August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Mars, Phobos and Deimos, 11.30pm August 1st.  Mars showing the south pole and Helas Basin, bottom and lower right.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

By mid-month, Mars has dimmed to -2.5 mag and now shows a 23.4 arc second disk. It now stands just over 12 degrees high as it transits, which occurs at just after 11.30pm BST (from 51 degrees N). 


Mars ends its apparent retrograde cycle within the ecliptic - appearing to move west within its orbital plane as it appears from Earth (rather than the more regular creep eastwards which most planets appear to make) around the end of August and as it does crosses briefly into eastern Sagittarius. As Mars' retrograde path appears to end, the planet will climb further north. By the 31st, Mars will be at -2.1 mag and 20.9 arc seconds across. It will now stand 12 2/3 degrees high at transit (from 51 degrees N), at 10.29pm BST.





At the beginning of the month, Jupiter is a -2.1 mag target in Libra and displays a disk of 37.8 arc seconds across. The planet will stand just over 23 1/2 degrees high as it transits, which will occur at 7.06pm (BST, from 51 degrees N).


Jupiter, having reached the end of its retrograde path in the sky for this year in early/mid July, as returned to prograde direction - west to east within the ecliptic. Due to this change, the planet is sinking further south and will continue to gently lose altitude from a northern hemisphere perspective. 


Mid-month finds Jupiter having faded fractionally to -2.0 and now presenting a 36.3 arc second diameter disk. Jupiter rises at around 1.34pm, transiting around 6.16pm (BST, from 51 degrees N), when the planet will be just over 23 degrees high in the south. Jupiter will set at just before 11pm, meaning the window for evening observing is starting to shut.  Jupiter is joined in loose conjunction in the sky on the evening of the 17th August, when the two bodies will be around 4 3/4 degrees apart in the sky at sunset.


Jupiter and the Moon in conjunction, early evening, 17th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Jupiter Io and GRS transit, early evening, 18th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

The 31st sees Jupiter having contracted a fraction to 34.8 arc seconds across and as a result has faded a tad to -1.9 magnitude. The planet now rises at just after 12.42pm (BST) and transits at 5.20pm, when it will stand just over 22 1/2 degrees high in the south (from 51 degrees N).  Jupiter will now set at just before 10pm (again, from 51 degrees N).





Saturn is well-placed for evening observation during August, rising at  just past 6.30 (BST) and transiting around four hours later. At +0.2 magnitude and 18 arc seconds across Saturn should make a worthwhile target for observation during the month. While rather poorly placed for those of us in the temperate northern hemisphere, the ringed planet is a joy to observe, no matter where on Earth you find yourself. With rings wide open and some easily found moons, Saturn always gives a good account of itself at the eyepiece. 


By mid-month, Saturn has shrunk a little to 17.7 arc seconds diameter, causing it to fade somewhat to +0.3 magnitude. 


Saturn and Inner Moons, transit point from UK (9.36pm BST), 15th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

By the 31st, Saturn is +0.4 mag and 17.3 arc seconds across. It will rise at just past 4.30pm and transits at 8.31, when it will stand around 16 degrees high in the south (from 51 degrees N).



Uranus and Neptune


The outer planets are both seen at their best in the morning, though both now rise in the late evening in early August (from a temperate northern hemisphere perspective). Given both the outer planets' respective brightness (+5.8 mag in the case of Uranus; +7.8 in the case of Neptune), optical aid will be realistically needed to observe both (though technically Uranus is a naked eye target under ideal circumstances). 


Relative positions of Uranus and Neptune, 15th August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

Uranus is found in western Aries throughout August and is joined in  the same are of sky as the waning crescent Moon on the morning of the 4th, when it passes south of the planet by 5 degrees. 


Neptune is located in Aquarius and rises earlier than its neighbour. Towards the end of the month, on the morning of the 27th, the Full Moon will be found around 6 degrees south of Neptune's location in the sky. While scattered light from our natural satellite will possibly make observations of the solar system's outer planet a challenge, the Moon provides a useful signpost in the early morning sky. The end of August finds Neptune a week from opposition - though as ever, due to the vast distance between us on Earth and the edge of the solar system, this makes little difference to the outer planets' brightness or size. 



Visible from the much of the Northern Hemisphere all night, periodic comet 21P/Giacobini-Zinner will be brightening quite rapidly during August. Starting its course through Cassiopeia, the comet will head eastward, crossing over into Camelopardalis on the 19th. By this point the comet may be skirting the limits of technical naked eye brightness - though will in all likelihood need a dark sky, little Moon and at the very least reasonable binoculars to see it. Certainly, the second week of August, when the Moon is New, represents one of the best times to attempt to spot this comet. By late August, 21P will have dipped briefly into Perseus before ending the month a little to the west of Capella in Auriga. Although now brighter, with the Gibbous phase Moon in nearby Cetus, the comet will be a more difficult target.  Early September will see Giacobini-Zinner reach peak brightness, though it will head south rather rapidly after the end of August. So if you’re in the northern hemisphere, make the most of it while you can. 


Giacobini-Zinner path August 2018.  Comet position correct for 1st August. Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

At time of writing, comet C/2017 S3 PanSTARRS is undergoing its second major outburst and has brightened by a significant margin.  The comet is still relatively faint, but if further outbursts occur, it could reach technical naked eye visibility in the first week of August.  It is reported from several sources that it is believed the comet is a visitor form the Oort Cloud and it is unlikely it has visited the inner solar system before, which minimises the potential for greater outgassing.  However the recent outburst leave us hoping that when the comet reaches perihelion at only 0.2AU from the Sun in mid-August, more may come from this comet.  It will be very close to the Sun from the second week in August (and lost in the morning twilight), so the beginning of the month is the only chance we will have to observe the comet in August, as it dives south through Gemini and Auriga (not too far from Giacobini-Zinner, in fact).

C/2017 S3 PanSTARRS path, August 2018. Comet position shown 1st August.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,


Another. PanSTARRS survey comet, C/2016 M1 will continue to give a good showing throughout the month for readers in the southern hemisphere, as it tracks through Circinus into Centaurus.  At the end of August it will be found near the two bright stars Rigel Kentaurus (otherwise known as Alpha Centauri) and Hadar (Beta Centauri).  This comet will be strictly a binocular or telescopic target though and invisible to those in much of the northern hemisphere.


There is still more to come from a cometary dimension with the return of periodic comet 46/P Wirtanen, which will make a close approach to Earth in November and December of this year.  We will cover this comet in later sky guides.





It wouldn’t be August without the Perseid meteor shower, which actually run from mid-July to late August.  They will reach their peak on or around August 12th.  Last year’s shower peaked with a zenith hourly rate of around 120 meteors and this year is expected to put on a slightly less impressive show, with aZHR of about 60-70 expected.  However, unlike last year, this year, the eternal nemesis of meteor observation, the Moon, won’t be around to spoil the party.  At New phase around the shower’s peak, the Moon will be safely put of the way.  As ever, the opportunity to photograph the shower shouldn’t be neglected - just make sure you’re in the darkest accessible area whilst attempting to capture the best of the Perseids.  Even if you are in the centre of cities, the brightest of the Perseids will cut through the worst light pollution, with many peaking in the minus magnitudes - meaning they will (briefly) be as bright as the brighter planets.


Perseid meteor over SW London.  Image Credit: Kerin Smith

Photographic recording of the shower requires a regular DSLR, with a wide angle lens, set to a reasonably high ISO (800+)  - this will undoubtedly pick up at least a couple of bright examples of the Peseids during an evening's worth of timed exposures. Multiple exposures of 30 seconds-or-so - depending on your sky conditions - will be more than adequate to pick up some Perseids over the space of a couple of hours.  Just make sure you have plenty of memory in your camera and that your batteries are fully charged prior to any attempt.



Deep Sky Delights - Climbing the Spine of the Milky Way 


Last month we looked at the expanse of Ophiuchus, with its riches of Globular clusters.  This month we move eastwards and then climb the spine of the Milky Way Galaxy Northward from its central bulge and explore some of the plentiful objects along this track of sky.  


The first constellation we come to is the diminutive Scutum, The Shield.  Scutum contains two objects of note, both open star clusters, the fainter M26 and the magnificent M11, or Wild Duck Cluster.  M26 is +8.00 mag and 7 arc minutes in diameter and is not the brightest of largest cluster in the area.  This is largely thought to be the result of interstellar matter obscuring part of the cluster - a reasonable common event for objects located on or near the plane of our galaxy.  If this material was not present it is likely M26 would appear bigger and brighter than it does to us.  Binoculars will pick it out and small telescopes will show its 30-or-so members well.  M26 is thought to lie around 5200 light years away.


M26's neighbour, M11 is to be found just under 3.5 degrees to the NE.  Whereas M26 is rather diminutive, the Wild Duck Cluster, as it is commonly known, is a lovely, rich object of +5.80 mag and 32 arc minutes across.  The major part of the cluster takes up an area roughly a third of the diameter of the Moon in the sky, making it a prominent feature in this area of sky.  M11 was discovered in 1681 by German Astronomer Gottfried Kirsch and included as an original Messier object in 1764.  It was the noted observer Admiral Smyth who first suggested the "Wild Duck" moniker - describing the fan shaped structure as resembling "a flight of wild ducks".  If examined in a telescope or larger binoculars, the "V" shape of the cluster seems to point in an Easterly direction, though it is not particularly well defined.  M11 is supposed to be about 250 million years old and thought to be around 6000 light years distance.  Its total of stars is thought to number just shy of 3000, though only 500 of which will be visible to amateur instruments.  It is not an object that should be missed in any type of instrument.


M11 - European Southern Observatory. Creative Commons.


Moving Northward from Scutum, we come to the major constellation of Aquila, The Eagle.  Despite its size and prominent position along the plane of there Milky Way, this constellation is curiously lacking in major Deep Sky objects.  The only one of great note is the interesting NGC 6741, otherwise known as The Phantom Streak.  This object is a planetary nebula of +11.69 mag and diminutive in size (as many planetaries are), at just 0.1 arc minutes across.  Looking like a ghostly parallelogram, the Phantom Streak is not an easy object, but its cocoon-like structure can be discerned by those with access to larger telescopes.  It is a rewarding find for those with the ability to find it.  The distance of NGC 6741 is not certain.  Some sources list it as lying 7000 light years distant, though others think it a closer object at around 5000 light years from us.  The Phantom Streak is notable for the possibility that its central star, a white dwarf remnant of a star much like the Sun, may be running out of hydrogen fuel and its dropping in luminosity.  This means the Phantom Streak may not be visible in its present form for much longer - a sign we live in a dynamic Universe.  Catch it while you can!


NGC 6741 - HST image.  Public Domain.


Moving up past Altair (Alpha Aquilae), the bottom-most star in the famous "Summer Triangle" (which also contains Vega and Deneb in Lyra and Cygnus respectively), we take a brief dog leg East into the tiny constellation of Delphinus, The Dolphin.  This lovely little collection of stars, though not especially bright, can easily be made out under dark conditions.  Delphinus' kite-shaped arrangement of four stars and the Dolphin's tail marked by the prominently blue Epsilon Delphini is unmistakable.  


Delphinus contains two globular clusters - nether particularly bright, but worth seeking out nonetheless.  NGC 6934 is the more Southerly and is found just under 11 degrees almost due east of Altair.  At +8.8 mag and 1.4 arc minutes in diameter it is hardly prominent, but is location in the rich star fields of the Milky Way go someway to explaining this.  Small telescopes show the cluster as a soft, rather indistinct ball of light, but larger instruments will be needed to show the scant detail it offers up to observers.  Lying over 50000 light years away, NGC 6934 was one of William Herschel's many discoveries - he first catalogued it in 1785.


NGC 6934 - HST image.  Public Domain.


Herschel also discovered NGC 7006 which is located some 11 degrees to the NE of NGC 6934.  At +10.56, it is one of the fainter of our galaxy's globular clusters. This faintness is understandable when one considers NGC 7006's distance - an amazing 135,000 light years hence.  This cluster is described by various observers as quite comet like in appearance - a condensed central region and a halo of stars are not as distinct as they are in its neighbour. A very large telescope of 16+ inches aperture will be needed to resolve individual stars in this challenging target.


NGC 7006 - HST image.  Public Domain.


Delphinus also contains a good planetary nebula:  the Blue Flash, or NGC 6905. This is more easily seen in small telescopes than either of the globular clusters previously mentioned.  Indeed, it is often overlooked, due to its proximity to the nearby M27 (more of which later), but the Blue Flash deserves more observation.  A blue-white ball of light, with extending lobes either side, NGC 6905 is +10.89 mag and  0.8 x 0.6 arcminutes in dimension and lies 2200 light years away.  Larger telescopes will start to pick up more of the object's uneven shape and central star.  It seems decidedly egg-shaped to some.


NGC 6905  HST image.  Public Domain.


Just under 7 degrees to the west of The Blue Flash, over the border into Sagitta, The Arrow, sits another globular cluster - M71.  


M71 - HST image.  Public Domain.

Discovered in 1746 by Philippe Loys de Cheseaux, M71 is a very loose globular, which was perhaps understandably classed as an open cluster for a considerable amount of time.  Binoculars show it well, but smaller telescopes will start to resolve it into stars.  At 3.3 arcminutes diameter and +8.18 mag, M71 is a curious beast: its spectral makeup and spread of differing star types is much more suggestive of an open cluster, though observations of the radial velocities of its constituent stars have pointed to its globular nature.  It is thought to be particularly young for a globular cluster, being "only" 9 billion years of age.


Moving further Westward, over the border into Vulpecula, The Fox, we come to one of the most celebrated clusters in the whole sky - Collinder 399, otherwise known as The Coathanger, for obvious reasons!  The asterism of The Coathanger contains ten bright stars, one of which is an orange-yellow colour, which contrasts nicely with the blue-white of the other nine.  A perennial binocular favourite, The Coathanger is a large object at 89 arc minutes diameter is best seen in widefield instruments at low powers.  Its unlikely appearance always raises a wry smile, as it is one of the sky's greatest practical jokes.


The Coathanger, Collinder 399.  Image created with SkySafari 5 for Mac OS X, ©2010-2016 Simulation Curriculum Corp.,

From the ridiculous to the sublime, the next object is one of the best examples of its type in the entire firmament - M27, The Dumbell Nebula.  This planetary nebula is to be found 8 1/3 degrees to the east of The Coathanger and is a richly rewarding object to observe in any telescope.  Small telescopes show it as an elongated glowing box.  Larger apertures show more and more of the distinctive "apple core" shape.  Long duration exposure images show the whole object, including its ghostly outer layers, beautiful colours and complex internal structure.  The Dumbell is a true Messier object, as it was discovered by Charles Messier in 1764 and at about half the diameter of the Moon and +7.09 is easily one of the most prominent examples of its kind in the sky.


M2.  Image Credit: Mark Blundell.

We see M27 from the side on - hence its less-than-planetary shape.  Were we observing it from a polar viewpoint, it would appear ring-like.  But we are fortunate that the inner structure of the nebula is so well-defined from our perspective.  M27's distance is heavily debated, but now appears to be around 1200-1700 light years away.  Its age is thought to be relatively young - 3-4000 years-or-so.  It is an easy object to locate and should not be missed by any observer.

 NGC 6885 is another inhabitant of Vulpecula and lies 4 2/3 degrees NE of the Dumbell.  It is a +8.10 open cluster, around 20 arc minutes in size.  Although not exceptionally bright, NGC 6885 is easily located in binoculars and is probably best-seen in a large pair.  This cluster contains over fifty member stars and has distance of around 1900 light years.

 Eight and a half degrees NE of NGC 6885, across the border into Cygnus is the enchanting target of the Veil Nebula.  The Veil Complex – NGCs 6960, 6974, 6979, 6992 and 6995 in Cygnus is a famous Supernova remnant, spread out over six times the diameter of the Full Moon.  At combined brightness of +5 mag, The Veil can supposedly be glimpsed with the naked eye under truly exceptional conditions, but is much more likely to be seen (and better observed) in large binoculars and telescopes.  The veil lies underneath the wing of Cygnus, close to Gienah (Epsilon Cygni). The brightest section this nebula is NGC6960, otherwise known as The Witches’ Broom, due to its obvious broom-like shape, which reveals itself best in long duration exposures.  NGC6960 has the star 52 Cygni apparently buried within it (it is in fact at least 10 times nearer to us), making this part of the nebula an easier target to find with non-Goto scopes.  The Veil responds terrifically well to the OIII filter – indeed, it is almost the best-responding nebula to this particular narrowband wavelength.  This beautiful structure can be seen in all manner of telescopes, but large instruments with low power, widefield eyepieces present it spectacularly well.


The Eastern Veil Nebula.  Image credit: Mark Blundell


Drifting Westwards, past one of the finest double stars in the entire sky, the Creamy Yellow and Electric Blue of Albireo (Beta Cygnii), just across the border into Lyra, The Lyre, sit two notable objects, the first of which is M56, which lies roughly equidistant between Albireo and Sulafat (Gamma Lyrae).  At +8.27, it is of similar brightness to  the aforementioned M71, though at 2.2 Arcminutes diameter – when compared to the larger M71 at 3.3 Arcminutes in size – is slightly more condensed and appears brighter.  Indeed, both objects would possibly appear more prominent were they not lying so close to the axis of our Galaxy and therefore obscured by parts of the Milky Way. 


Roughly halfway between Sulafat and the neighbouring naked eye variable star, Sheliak (Beta Lyrae) sits one of the showpieces of the sky, the wonderful M57, the Ring Nebula.  M57's enduring popularity as a Deep Sky target may be partially down to the ease with which its location is to be found.  Looking like an elongated smoke ring drifting through space, the Ring Nebula is perhaps the archetype of all planetary nebulae.  Discovered in 1779 by the astronomer Antoine Darquier de Pellepoix, Messier was hot on his heels and independently discovered it a matter of days afterwards.  Rather disappointing in binoculars, yet easily spotted in most telescopes due to its comparatively high surface brightness, M57 takes magnification and filtration (especially the OIII filter) extremely well.  Naturally, the larger the telescope you point at it, the more the keen observer is likely to see, but those with smaller telescopes will not be disappointed as long as you keep magnification up.  


M57 - HST Image.  Public Domain.

M57's distance is still up for debate, modern estimates of the central star put it at about 1400-4000+ light years away - quite a variation!  It is thought is the former figure is the more correct, M57 is about a light year across from widest point to widest point and is a cylinder shape which we see from the end - quite the opposite, in fact, to M27's aspect.  It is thought that The Ring Nebula is around 5-8000 years old.


Back into Cygnus, climbing higher North up the spine of the Milky Way, we come to a reasonably diminutive, but nonetheless fascinating object:  NGC 6888, The Crescent Nebula. a bright, compact nebula, which is the expanding shell of a Wolf-Rayet Star (HD 192163), which is steadily shedding its outer layers.  The nebula glows due to the fact that it is gas is superheated by the collision of the boundary layer of a faster-moving inner solar wind, meeting a less energetic layer of solar wind formed when the gaseous layer of HD192163’s former outer atmosphere was ejected in its previous red giant phase.  This bow shock is about 25 light years across and appears to us as a crescent shape, glowing at +7.40 mag.  The “surface” of this crescent is incredibly detailed and its complicated texture can be noted in larger telescopes using OIII and UHC filtration.  Much beloved of Astrophotographers, the Crescent Nebula is a rewarding target for imagers.


Crescent Nebula, NGC 6888.  Image Credit: Mark Blundell


Right next door to the Crescent, clustered around the star Sadr (Gamma Cygni) is the vast expanse of the Gamma Cygni Nebula.  Glimpsed in large binoculars and telescopes from an appropriately dark locale, IC 1318, as it is otherwise known, is a huge patch of red nebulosity, slightly larger in dimensions than the Veil.  However, this nebula is very spread out, so its surface brightness is inherently low.  It is best visually isolated with H-Alpha Filters, but is more easily captured in long duration astrophotography.  The Gamma Cygni Nebula reaches out behind the Crescent and the star that is takes its name from.  Sadr is around 750 light years away, whereas estimates for the distance of the nebula vary wildly from 2000-5000 light years distance.


Further up the spine of Cygnus, just beyond its principal star, Deneb, is another vast nebula system: the North American Nebula (NGC7000) and tucked underneath it, the Pelican Nebula (IC5070).  Of the two, the North American is undoubtedly brighter (at +4 mag, compared to the Pelican’s +8 mag) and can be seen very well in large binoculars from a dark site.  An OIII or H-Beta filter can be used successfully to enhance NGC7000 in widefield telescopes, but the complex does not respond well to magnification. Both nebulae are part of the same gas cloud, which may be ionised by emissions from nearby Deneb.  If this is the case, their distance would be in the region of 1800+ light years away from our Solar System.


The "Mexico" section of the North America Nebula, NGC7000.  Image Credit: Mark Blundell.


Last but not least is a much smaller object, the Blinking Planetary or NGC 6826.  This nebula is 2.1 arc minutes in diameter and located towards Iota Cygni.  Dimensionally, NGC6826 is fractionally larger than the Ring Nebula and about the same brightness.  The “blinking” nature of this planetary is caused when an observer stares at the nebula’s central star, at medium to high power, this overwhelms the eye and the nebula fades from view.  When you look away to the nearby +8.5 magnitude star in the same field, the nebula reappears.  This is not a unique phenomenon and is noted in other compact planetary nebulae with prominent central stars, but is best seen in the Blinking Planetary.  Visually, the NGC6826 present two brighter regions on either side of its disc. These regions are Fast Low-Ionization Emission Regions or FLIERs for short.  These FLIERs are parts of the planetary formation which are expanding at extreme speeds in comparison to the surrounding nebula.  It is postulated that these areas are so dense that the ionising effect of the ultraviolet radiation emitted from the parent star cannot penetrate them.  The Blinking Planetary and the Saturn Nebula are two of the best known examples of planetaries that exhibit these FLIERs.


NGC 6826 - HST Image.  Publc Domain.


Text - Kerin Smith