Sales & Advice 01342 837 098
Shopping Basket
0 item(s) - £0.00
You have no items in your shopping cart.


Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

Telescope House September Sky Guide

September brings the Autumnal Equinox for the Northern Hemisphere and the Vernal, or Spring Equinox for this in the Southern Hemisphere. This year these events occur on 22nd of September, where for a brief period for day and night are of nearly equal length. This equality of dark and light really depends on where you find yourself, as there are few places on Earth on the 22nd September where day and night are truly equal. However, crucially, the 22nd marks the point where the Sun crosses into the southern celestial hemisphere - which results in increasingly more hours of darkness than light for those of us in the Northern Hemisphere; and of course increasingly less darkness for those in the Southern reaches of our planet. Many people for whom astronomy is of no more than at most a passing interest will bemoan the lack of daylight in the Northern Hemisphere - the same cannot (in all probability) be said of the many readers of this Sky Guide. For us astronomers, the dive towards Winter does have its perks. 


As ever, there's a lot to see in skies above us this month...


The Moon 


The Moon begins September a little after First Quarter, low (from a Northern Hemispherical perspective) amongst the stars of Sagittarius.  By the evening of the 6th, it has reached Full in Aquarius, around 7 1/2 degrees to the east of the distant planet Neptune. 


On the early morning of the 12th September, the moon begins one of its regular jaunts through the Hyades in Taurus, occulting many members of the star cluster as it goes.  If you brave the small hours, or are up early, this is best seen through binoculars or a wide field telescope.  It’s always a lovely sight and one worth photographing as well.


The next day on the 13th, the Moon has reached Last Quarter in Taurus, sitting high in the morning sky before sunrise. This is an example of the high morning crescent phase of the autumn skies and offers some of the best opportunities to view the Moon - particularly its western limb, with our satellite high in the sky in the most northerly part of the ecliptic from the northern hemisphere. 


On the morning of the 18th, the razor thin (4.6% illuminated) Crescent Moon will sit just below Venus (by around 3 degrees) before sunrise.  The pair will also be joined by Mercury and Mars, situated around 8 degrees below the Moon.


The Moon, Venus, Mercury and Mars, Sunrise 18th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

New Moon occurs on the 20th with the Moon in Virgo, making this part of the month an ideal time for observation and astrophotography of fainter deep sky objects (more of which later in this article).  Thereafter, our natural satellite goes through its Waxing Crescent phases low in the sky amongst the stars of Libra, Scorpius and Ophiuchus (from a Northern Hemisphere perspective).  This is the point in the year that the Moon at Evening Crescent phase appears high in the sky for observers in the Southern Hemisphere - the “Southern High Crescent Phase - which makes for excellent viewing conditions from temperate southern parts of the planet.


The Moon joins Saturn in the early evening sky in Ophiuchus on 26th of September, the pair separated by under 4 degrees.  This makes identifying the fainter planet much easier for beginners, sitting as it does just a little to the SE of the thin Crescent Moon. 


The Moon reaches First Quarter phase in Sagittarius on the 28th, before ending September at Waxing Gibbous phase in Capricornus on the 30th.




The Innermost planet starts September as a very dim +3.0 mag morning target in Leo, rising just over an hour and a half before the Sun.  The reason for the planet’s current lack of magnitude is its phase, which is a very thin 6.2% illuminated crescent.  As ever, with Mercury, this situation doesn’t last long - by the 7th, its phase has increased to 24.2% illumination and the planet is now at a healthier +0.8 mag, standing at around 12 degrees altitude in the east at sunrise (from 51 degrees N).  


Mercury reaches maximum elongation from the Sun on the 12th and continues to increase in brightness.  By the 15th, Mercury is -0.6 mag and 59.2% illuminated, standing 14 2/3 degrees high in the east at sunrise (again, from 51 degrees N).  This is one of the best times of the year to observe Mercury, so getting up early will have its benefits.  On the 16th/17th September, Mercury will be in very close conjunction with the much fainter Mars - the two separated by just over 3 arc minutes at their closest.  While those of us in Europe will miss the closest part of this conjunction, the mornings of the 16th and 17th will see the two planets around 27 and 20 arc minutes apart - still close enough to get into the field of view of a moderately-powered telescope.  Mars at +1.8 and 3.6 arc seconds across, will be a disappointing target, emerging as it is from its recent superior conjunction with the Sun.  Mercury, at 6.5 arc seconds diameter and -0.7 mag will be much the more noticeable of the two.  It will be a challenge to observe this conjunction in the glare of the dawn, but a rewarding one if you do.


Mercury, Sunrise 24th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

By the 21st, Mercury sits just under 12 1/2 degrees high in the east at sunrise and shines at an impressive -1.1 mag.  At 5.7 arc seconds across and 81.3% illumination, it should be about as impressive a sight as Mercury often gets at this point in time. Although Mercury gets progressively brighter still as the month continues, ending September at -1.3 mag, the-Janet’s separation from the Sun gets progressively smaller and smaller.  By the 30th, Mercury is barely 7 degrees away from the Sun and will be difficult to pick out in the morning glare.




Like Mercury, Venus Is a morning object during September and begins the month about a degree to the west of the Beehive Cluster, M44, in Cancer.  Shining at a dazzling -4.0 mag and appearing at an 83.8% illuminated phase, some 12.4 arc seconds across.  Venus will stand around 25 3/4 degrees high at sunrise on the 1st and will dominate the sky around it.


Venus and the Beehive Cluster, early moring, 1st September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

By mid-month, Venus has increased its phase to 87.3%, but decreased its size to 11.8 arc seconds across.  It has dipped only slightly in brightness to -3.9 mag by the 15th.  Standing just under 24 degrees high at sunrise it is still the easiest object to spot in the east in the dawn sky and should be unmissable.  As previously mentioned, the very old Moon joins Venus in a loose conjunction on the morning of the 18th, which should make a pretty vista to observe.


By the end of September, Venus has dipped towards the Sun somewhat, standing just under 21 degrees high at sunrise. Although the planet's phase has increased to 90.6% illumination, the diameter of Venus has shrunk further to 11.2 arc seconds, as it pulls further away from us. However, the planet's area doesn't change significantly with increase in phase keeping pace with decrease in angular size. Venus remains a very bright -3.9 mag on 30th September. 




Although Mars as reported earlier is in extremely close conjunction with Mercury this month, that's where the interest ends as far as the red planet is concerned. At +1.8 mag, a mere 3.6 arc seconds across and separated from the Sun by just 11 2/3 degrees, Mars is a poor target for meaningful observations.  Having just emerged from superior conjunction, this is hardly surprising. 


By September's end, while Mars hasn't become significantly brighter or much larger, it has increased its separation from the Sun to 21 1/2 degrees and sits around 18 degrees high at sunrise (from 51 degrees N).  The planet sits a little over 3 degrees from the much brighter Venus on the morning of 30th September. 




The Solar System's largest planet begins the month as a -1.7 mag, 32.1 arc second evening object. Separated from the Sun by just over 42 1/2 degrees, Jupiter is rapidly heading Sunward and is only visible for just over an hour after sunset from temperate northern latitudes - though those in the equatorial parts of the Earth will be able to observe it for a little while longer. 


As September continues, the window for evening observation of Jupiter narrows. By the 15th, the planet will set under an hour after sunset. By the 30th, this time has decreased to under 40 minutes and with Jupiter sitting just over 5 degrees in the sky at sunset (from 51 degrees N), it is safe to say, for those in temperate locations on Earth, evening observation of Jupiter is drawing to an end. Of course, daylight observations of Jupiter are possible, but with the planet around 20 degrees from the Sun, extreme caution must be exercised when attempting these. 


Jupiter, Sunset, 15th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

Jupiter, at the end of September, is less than a month from superior conjunction, so it won't be long before the giant planet finds itself in the morning sky again. 




Further east in the ecliptic than its neighbour Jupiter, Saturn is still well-placed for evening observers during September. At just past transit point in the south at sunset, Saturn is +0.5 mag, with a 16.9 arc second diameter.  Setting at around 11.40pm (from 51 degrees N), if you have a reasonable S/SW/W aspect, the Ringed Planet should be top of your list for observation in the early evenings. Naturally, as covered in previous Sky Guides, Saturn is very low in the ecliptic, from a Northern Hemisphere perspective, but is aways worth seeking out, wherever you find yourself. 


By mid-month, nothing much has changed as far as Saturn is concerned: it's still +0.5 mag and has shrunk by a very small amount to 16.6 arc seconds across. However it now sets at 10.45pm (from 51 degrees N), and while this is somewhat offset by the Sun setting earlier and earlier each night, it is a sure sign that, much as we've experienced with Jupiter this month, Saturn's days as an evening object are numbered. It is still a while before Saturn's superior conjunction in December, so the planet will be observable for a while yet.  As previously mentioned, Saturn and the First Quarter Moon have a rendezvous on the evening of the 26th, with Saturn to be found a little to the SE of the Moon in the sky. 


Saturn and the Moon, evening, 26th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

By 30th September, Saturn remains at +0.5 mag and is now 16.2 arc seconds diameter. The planet now setts at 9.49pm (again, from 51 degrees N). 


Uranus and Neptune 


With the loss of the easily-observable Jupiter and the closing window for Saturnian study, the outer gas giants, Uranus and Neptune somewhat take over as evening planetary targets during September. Although profoundly dimmer than Jupiter and Saturn and more difficult to identify and observe, they are both worth seeking out in telescopes or binoculars (though Uranus can be glimpsed with the naked eye under reasonably dark conditions).


Uranus, Neptune and the Moon, 7th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,

Of the two outer planets, it is Neptune that comes to the fore this month as it comes to opposition on September 7th. Sitting in Aquarius at +7.8 mag, presenting a diameter of 2.4 arc seconds across, even at its best, Neptune is a challenge to observe.  The constellation it is resident in is hardly on of the brightest in terms of stars, but there are a few handy pointer to work out what area of sky Neptune is in.  If you trace a line from the bright (+1.23 mag) southern star, Formalhaut, Alpha Piscis Austrini) in the constellation of Piscis Austrinus, the Southern Fish, up to Markab, (Alpha Pegasi) the bottom right star (from a Northern Hemisphere perspective) in the Square of Pegasus - the are of sky Neptune can be found in is about half way along this line.  The nearest reasonably bright star in Aquarius near to Neptune’s position is Hydor (Lambda Aquarii), a +3.75 mag star, which lies just over a degree to the west of Neptune. 


Once located, Neptune seems to resemble a planetary nebula, or out of focus star in small telescopes.  It definitely has a blue hue to it, which is more pronounced the larger the aperture instrument you observe with.  In larger telescopes it is possible to observe Neptune’s large satellite Triton, thought to be a captured Dwarf planet, due to its unusual retrograde orbit and appearance.  Triton orbits Neptune roughly once every six days.  At +13.6 mag on opposition night, it will require reasonable aperture and conditions and high magnification to pick out visually, but is a relatively easy target to image.  Neptune’s host of other satellites, now numbering 14 in total, are much more challenging to detect.  The second to be discovered (in 1949), Nereid, is a dark, irregularly-shaped body, with a current magnitude of around the 19th magnitude.  The slightly larger Proteus, which orbits much further in to Neptune, had to wait until the arrival of Voyager 2 to the Neptunian system in 1989 to be discovered - so don't expect to be observing much beyond Triton, as far as Neptune's moons are concerned. 


Neptune rises at 7.25pm and sets at 6.17am the following morning on the night of opposition (from 51 degrees N). 


The easier to find Uranus is resident of Aquarius' more easterly neighbour Pisces, rising and setting a little later than Neptune as a result. At +5.7 mag during September, the planet is technically a naked eye object, though you will need good skies, star charts and eyesight to see it with the unaided eye. 


Just like Neptune, Uranus does not have any major bright stars around it to help locate it at present - the nearest star of any significance is the rather feeble Omicron Piscis, shining at +4.26 mag. Although on the morning of the 9th September, the Moon provides a handy waypoint to locate the distant planet - Uranus sitting some 7 degrees above it (from temperate Northern Hemisphere locations), just before sunrise.   


Once found in a telescope or powerful binoculars, Uranus presents a green-gray disk, around 3.7 arc seconds in diameter. Experienced observers, with large aperture telescopes, utilising high magnification can sometimes detect striation and brighter parts of the Uranian disk, but those with smaller telescopes will have to make do with simply finding and identifying the planet. 


Uranus will be at opposition next month, so we will cover the planet and its moons in more detail in the next Sky Guide. 




With previously covered Comets C/2015 V2 Johnson and C/2015 ER61 PanSTARRS now on the wane, but still observable from the Southern Hemisphere and in Taurus respectively, our attentions turn to the newly-discovered Comet ASASSN (2017 O1). 


While the name of this comet seems somewhat sinister, in fact it's just an acronym for "All-Sky Automated Survey for Supernovae" - a project run by the Astronomy Dept. Of the Ohio State University, USA.  This consists of 8 robotic telescopes arranged in two groups of four at the Las Cumbres Observatory's Haleakalā facility in Hawaii and their Cerro Tololo location in Chile. 


While the primary function of ASASSN is to hunt for Supernovae all over the sky, the detection of comets as changeable objects within areas of study in the sky is an added bonus. C/2017 O1 is their first cometary discovery - and it seems to have the potential to be a good one. 


Although comets are notoriously difficult to predict, this comet should be a binocular object in September, possibly +7 mag, or even brighter - travelling through the stars of Taurus.  During the middle of September, C/2017 O1 will be found equidistant between the Pleiades and the Hyades star clusters. 

 C/2017 O1 ASSASN, early morning, 17th September.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,


Deep Sky Delights in Cepheus and Cassiopeia


Cepheus and Cassiopeia.  Image created with SkySafari for Mac OS X, ©2010-2012 by Southern Stars,


Cepheus is a large, though rather sparse (from a stellar magnitude point of view) circumpolar constellation which borders Ursa Minor, Draco, Cassiopeia and Cygnus. In sky lore Cepheus represents the King to Cassiopeia's Queen and the two of them were supposedly parents to adjacent Andromeda. All of the brighter stars of this particular constellation are located to in the southern part of Cepheus, the brightest of which is Alderamin, Alpha Cephei, Alderamin is a notable star, due to the fact that it is one of the closest bright stars to the northern celestial pole - in fact it will come within 3 degrees of the pole in 5,500 years time, due to Earth's axis' precessional "wobble". Allthough not especially bright at around +2.47 mag, Alderamin is quite a nearby star, thought to lie around 49 light years from our solar system. Although sharing some main sequence characteristics with stars like the Sun, Alderamin may be on the cusp of becoming a red giant, much as our Sun will after it runs out of Hydrogen as its primary nuclear fuel. It is a mysterious star which emits much more X-ray radiation than it should. The process behind this is not well understood, but may be down to an unseen companion star whipping up the upper layers of the primary star. Alderamin appears to rotate very quickly for its size - whereas our Sun will take around 40 days to revolve once, Alderamin rotates once every day! 

 Although Cepheus is not an especially prominent constellation in terms of bright stars, it is littered with nebulousity.  Just under 6 degrees to the north of Alderamin lurks a wonderful object - NGC7023, otherwise known as the Iris Nebula. Despite its nickname, the Iris Nebula is actually a collection of stars bounded by a reflection nebula. The NGC7032 catalogue number actually refers to the cluster of stars, rather than the nebulosity that surrounds it. The main central star of the cluster, V380 Cephei, is responsible for the main illumination of the nebula, despite its reasonably low brightness of +7.36 mag. 


Visually, the central, brighter part of the nebula is visible in reasonably small telescopes - and although none of the colour revealed in long duration astrophotos is visible, the central nebulosity takes on a delicate, layered quality. UHC filters and OIII filters will isolate some areas of visual nebulosity, though as this is a reflection nebula, rather than an emission object, the less harsh Skyglow and CLS filters are probably better for this particular target. As previously eluded to, imaging really reveals the iris-like nature of this nebula in all its glory - as shown by Mark Blundell's picture below. 


This object is a tricky one to image as the darker parts of the nebula really require quite a long exposure time in order to be shown at all. 


3 1/3rd degrees to the NE of the Iris Nebula is the star Beta Cephei, which is a variable star - though not the archetypal Cepheid Variable. For this, we must look towards Delta Cephei, which is the opposite corner of the "Square of Cepheus" to Beta. Delta Cephei's variability was discovered in 1784 by John Goodriche - a remarkable Dutch-born English Astronomer. Goodriche was born to a fairly wealthy family, but became profoundly deaf after an early childhood illness. In an age where disability was not viewed in the more enlightened way it is today, Goodriche was fortunate enough to be educated at the groundbreaking Thomas Braidwood Academy for the Deaf in Edinburgh and later at the dissenter's college Warrington Academy. After completing his education, he returned to his parents in York, where he was befriended by their neighbour and distant cousin, Edward Pigott. Nathaniel Pigott, the father of Edward had a great interest in Astronomy and sensing Goodriche's enthusiasm, Edward gave him a series of stars to observe. The Pigott's observatory was quite advanced for the time and gave Goodriche the opportunity to study numerous variable stars, one of which was Delta Cephei. Although many variable stars had been noted in the sky from classical times - the most notable of which being the classic eclipsing binary Algol, in nearby Perseus - variable star research was still really in its infancy. 


Edward Pigott was the first to observe what we now know as a Cepheid Variable, Eta Aquilae, but it was Goodriche that presented his theory on eclipsing variables (based largely on his observations of nearby Algol, in Perseus), to the Royal Society in May 1783. On the merit of this presentation, Goodriche was awarded the prestigious Royal Society's Copely Medal for "outstanding achievements in research in any branch of science" in the same year. He was elected a Fellow of the Royal Society in April 1786, but tragically died of pneumonia just a few days after this honour was awarded. 


Although Godriche got the eclipsing model of Algol correct, he could not have known at the time how different the mechanism of Delta Cephei's variability was - nor the far-reaching influence (no pun intended) that the greater knowledge of the class of what would become known as Cepheid Variables would have. The classical eclipsing variable is caused by a dimmer star passing in front of a brighter companion, dimming its light down somewhat. Cepheid Variables are very different: these are pulsating stars, which vary their brightness with their radial pulsation. The key to the usefulness of Cepheid variables is that their pulsation period is linked quite precisely - certainly in the case of classical Cepheids. So bright are Cepheids that by studying the variations in these pulses, it is possible to calculate with very reasonable precision the luminance of these stars - even over vast distances. The longer the period of the lighter stage of their variability, the more luminous they tend to be. It is by observations of these "standard candles" of the Universe that it was first possible to accurately estimate the distance of objects not only within the Milky Way, but much further afield. Cepheid Variables became the way in which the distance between galaxies and the vast scale of our immediate Universe was first calculated by Edwin Hubble in 1924, when after observing the Cepheid Variables within the Andromeda Galaxy, M31, he managed to work out that it was not an object within our galaxy, but considerably further away. 


Standard Cepheid Variables are ordinarily yellow supergiant stars which are typically 4-30 times the mass of our Sun and up to a staggering 100,000 times as bright. They are of spectral class F6-K2, which vary their radius by around 25% over a period of days to months. This variability is caused by layers of ionised Helium building up in the outside layers of these stars. This Ionised Helium becomes opaque, masking radiation from the interior of the star, which in turn builds up, expanding the opaque ionised layer until it cools, de-ionising the layer, which then becomes transparent, revealing the light from within, causing a dramatic increase in brightness. This transparent layer then collapses back towards the star's surface under gravity, after which it is heated and ionised again, thus refreshing the ionisation layer and starting the process off again. It is thought that this build up of Helium is indicative of the fact that Cepheids are running out of Hydrogen as their primary fuel and are thus entering into the last phases of their lives. There are also fainter Cepheid Variable II stars, which tend to be yet older and less energetic and also Anomalous Cepheids, which are rapidly pulsing stars and may well be younger than both type I and II populations. The relationship between type I and II Cepheid Variables was defined by the work of Water Baade in the 1940s, leading to a four-fold upwards revision of the distance from our galaxy to M31. 


Delta Cepheus itself varies in brightness in terms of magnitude from +3.6 to +4.2, over the space of just over 5 days. This variability is not slowly uniform - its decay is much longer than its subsequent increase in brightness. After refinement of its distance by observations over 200 years, it is now thought Delta Cepheus is around 870 light years away it truly is a remarkable star. Delta Cephei also has a companion star of around +6.3 mag, separated by about 41 arc seconds. 


 Just over 5° to the north of Delta Cepheus lies the Cave Nebula, otherwise known as Sharpless 2-155. A difficult visual object in all but the largest amateur telescopes, 

The Cave Nebula really comes alive in long duration exposures -particularly those photographs which are taken with hydrogen alpha filtration. The Cave Nebula has an apparent size 50 x 30 arc minutes and an apparent visual magnitude of +7.69 magnitude. It is so called because its red hydrogen gas cloud is bisected by a curving dark area giving rise to a perceived similarity to the entrance to a cave - and who are we to argue?  Lying around 2400 light years away, The Cave is thought to be around 70 light years across. 


Just over 12° to the north of the Cave Nebula lies very different nebula. This particular target is a planetary nebula, NGC 40, otherwise known as the Bow Tie. 

The Bow Tie Nebula, although apparently much fainter than its neighbour is in actual fact an easier target in telescopes. Although +10.6 magnitude, the Bow Tie Nebula has a tiny apparent size 0.6 x 0.6 arc minutes dimensions. This means that its surface brightness is comparatively high, a common trait for planetary nebula. Sir William Herschel discovered in NGC 40 in November 1788. A moderate-sized telescope will pick out the Bow Tie reasonably easily, a 10 inch + reflecting telescope of moderate power will show NGC 40 very well, and a UHC Filter will provide a higher contrast view of the nebula, picking out some of the delicate structure within and really showing the "Bow Tie" shape off well. Lying around 2700 to 3500 light years away NGC 40 is thought to be around one light years across. This is well worth finding in a telescope - especially if the Cave Nebula proves elusive! 

 Back South through the Cave Nebula, we arrive at the dual Star Cluster and nebulousity  of NGC7380, otherwise known as the Wizard Nebula.  This object is around the 7th magnitude in brightness and part of the nebulosity does appear in long duration images, like a figire in a pointed wizard's hat standing with their back to the viewer.  Se Mark Blundell's image below and see if you can pick the "wizard" out yourself.

This object is around 100 light years in diameter and lies over 7200 light years from Earth.  While this object photographs extremely well, it is perilously difficult to observe visually and requires large apertures, very favourable observing conditions and OIII filters to stand a chance of seeign the nebulosity.

Nine degrees to the west of NGC7380, we come to the last of Cepheus' rewarding deep sky objects, the fabulous nebula IC 1396, also known as the Elephant's Trunk, within whose borders lies the richly red Mu Cephei, otherwise known as the Garnet Star. IC 1396 is a massive cloud of nebulosity, some 170 x 140 arc minutes across and although it is listed as "bright" at +5.59 mag, though is very diffuse. A UHC filter will enhance the visual view of the Elephant's Trunk and an OIII filter will help to isolate the dark lanes in the nebula, the most major of which does resemble the prehensile trunk of an elephant - as displayed in Mark Blundell's image below. 


As with other diffuse nebulae, IC 1396 does really come into its own in terms of imaging - though those attempting to record IC 1396 photographically will need a fairly short focal telescope - preferably a wide angle lens in order to cram this 170 x 140 arc minute object in! A blue star, HD 206267 lies near the centre of this massive object and is responsible for the ionisation of the entire nebula. The outward pressure from the radiation of this huge star has compressed the interior of the nebula, forming globules of gas and dust that are in the process of forming stars. There are several very young stars which have just (cosmically speaking) started life within IC 1396 - they are under 100,000 years of age. It is unsure quite how large IC 1396 actually is - it is hundreds of light years in diameter and is thought to lie around 3000 light years from Earth. 

 Another well-photographed area of nebulosity in Cepheus is NGC7822 and the star cluster Berkley 59.  Around 3000 light years away, this young cluster and the nebulosity surrounding it show similar structures to IC1396, as aptly demonstrated in Mark Blundell's image below:



Mu Cephei, otherwise known as the Garnet Star, as mentioned previously, appears to lie within the nebula, but is now thought to be around 2000 light years further away. It is a massive and very red star, which is in the last stages of its life and is a prime candidate for Supernova at some point "soon" - though this could be in hundreds of thousands, if not millions of years time. If placed within out solar system, in place of our Sun, the outer edges of Mu Cephei would lie somewhere between Jupiter and Saturn's orbit and fit a staggering 1 billion stars the volume of the Sun inside its sphere. The star is ejecting its outer layers, which are drifting off and forming radial nebulosity around the system. Mu Cephei is yet another of Cepheus' variable stars, which varies from between +3.6 mag to around +5 mag every 2 to 2 1/2 years. It is also phenomenally luminous - some 100,000 times brighter than our Sun. We are fortunate that Mu Cephei is so far away from us, as when this star does eventually die, it will be problematic, to put it mildly, for any system within a 50-100 light years radius of the resulting Supernova. 


Across the border into Cassiopeia, lie two twin objects, the Heart and Soul Nebulas, otherwise known as IC 1805 and 1848.  These objects both have star clusters lurking within their boundaries which are possibly associated with the objects, though opinions seem to differ on this.  Whereas the Double Cluster in nearby Perseus is prominent from a visual perspective, these two objects, despite visual magnitudes of +6.5 mag, are much less so and require a decent sized telescope and access to UHC or OIII filters to see them well at all.  It is in Astrophotography that these extraordinary objects truly come alive, as long exposures reveal the intricate and beautiful nature of these nebulae.  The Heart Nebula does indeed appear heart shaped, though the Soul Nebula appears to be shaped more like a baby!  The Heart and Soul Nebulas lie 7500 and 6500 light years away respectively.


The interior of the Heart Nebula a pictured by Mark Blundell in the Hubble Pallette.

West of the Heart and Soul Nebulas are a collection of star clusters, of varying brightness and interest.  The rather obscure NGC 559 lurks to the North of the Cassiopeia "W" asterism, though at +9.5 mag is far from spectacular.  Much better is NGC 663, an open cluster of +7.09 mag which lies below Segin, the first star in Cassiopeia's "W".  This cluster is a good telescopic object of about 14 arc minutes diameter and lies about 8000 light years away from us.  This is a young cluster of non-supergiant stars, whose age is reckoned to be between the 12-25 million year mark.  It has been commented that it is hard to fathom why NGC 663 escaped Messier classification - as it is a prominent target.


A cluster which did not escape Messier classification in this area is M103.  This was the last object to be added to Messier's original list and is an easy find.  This +7.4 mag open cluster lies just 1.5 degrees NE of Ruchbah, or Delta Cassiopeiae, the bottom of the first "V" in cassiopeia's "W:.  M103 is a condensed cluster, being just 5 arc minutes across and lying around 8-9000 light years from us here on Earth.  This cluster has a distinct triangular or fan shape, which appears as a misty "V" shape in large binoculars.  Telescopes will show this cluster better, but it is less impressve than some of its neighbours.  This may be down to interstellar dust obscuring the light from many of its 170+ stars.  It has been speculated that M103 and NGC 663 were in some was misinterpreted and swapped around by Messier.  NGC 663 is in the same direction from Ruchbah as M103, so maybe this could be the reason for misinterpretation.  But others have countered that the primary aim of Messier's list was not the cataloguing of spectacular Deep Sky objects, rather those that could easily be confused as Comets.  In the case of M103, this does make sense.


A better cluster still is NGC 457, the Owl Cluster - so called because its two brightest stars appear like an Owl's eyes staring out from the darkness and the rest of the cluster can be seen as the owl's body.  Lying some 2 degrees South of Ruchbah, the Owl Cluster is a +6.4 mag object, comprised of over 100 stars and is an excellent target for larger binoculars and telescopes of all sizes.  Chains of stars protrude to the NW and S and E and its Northern boundary is marked by a distinct red star.  Lying 9-10,000 light years from us, the Owl Cluster should not be missed by any observer.  Herschel is listed as the discoverer of this cluster, but it is unlikely he was the first to observe it as it is so prominent.


Moving to the central peak of the "W" of Cassiopeia, we come to Gamma Cassiopeiae. This is an intensely energetic Blue sub-giant star which is located some 610 light years from us.  This star is hugely luminous, outputting some 40,000 times more radiation than our Sun.  Given this rate of luminosity and its sub-giant status, it will not be long-lived and is a prime, relatively nearby candidate to go Supernova.  It is also a variable star with an irregular variability - as recently as 1940 it dimmed to +3.4 mag, but now outshines both Alpha and Beta Casiopeiae at +2.18 mag.  Surrounding Gamma is the Gamma Cassiopeia Nebula, which consists of two sections, IC 59 an IC 63.  These are two sections of a reflection nebula, which is illuminated by Gamma Cassiopeiae and may well have emanated from the star itself.


Large telescopes of 12-inch class and above will show this nebula from a dark site, though IC 63 is undoubtedly the brighter part.  As a reflection nebula, the Gamma Cassiopeia Nebula does not readily respond to filtration.


Gamma Cassiopeae is remarkable for being unnamed - that is until (apocryphally) Astronaut Virgil I "Gus" Grissom decided to nickname it "Navi" - which is Ivan, his middle name, spelt backwards.  The nickname stuck amongst the US Astronauts of his era and is still in unofficial use today.


Moving down to the bottom of Cassiopeia's second "V" we come to Alpha Cassiopeiae, or Shedar.  Johann Bayer listed Shedar as Cassiopeia's principle star, in his early 17th Century star atlas "Uranometria" - though it is clear that Beta and Gamma have often surpassed Shedar in brightness.  1 and 2/3rds degrees East of Shedar sits NGC 281, otherwise known as The Pacman Nebula, due to its passing resemblance to the titular arcade game character. Pac Man was always yellow in the game, whereas NGC 281 appears red in long duration photographs - yet the resemblance is undeniable.  The Pac Man Nebula seems to be happily munching his was through the surrounding starfields, though there are no Blue Ghosts in hot pursuit of him.  This nebula is around the +7.4 mag level of brightness and around the size of the full Moon in the sky (30 arc minutes in diameter).  With a 10-inch class scope and either a UHC or an OIII filter, NGC 281 can readily be observed - especially its dark inner lanes, which are especially evident in the OIII filter.  The Nebula is about 10000 light years away and was discovered by American Astronomer E.E. Barnard (he of Barnard's Star fame), in 1883.


The Pacman Nebula by Mark Blundell.

Just under 3 degrees from Caph, or Beta Cassiopeiae, lies the lovely open cluster of Caroline's Rose, or NGC 7789.  At +6.69 mag, it is again shocking it was not listed as a Messier List object.  It is named for its discoverer, Caroline Herschel, the sister of William Herschel, his sometime assistant and very experienced Astronomer in her own right.  The Rose part of this cluster's popular name comes from the impression the loops of stars and alternating dark lanes of this cluster give of a White Rose's petals - it is indeed a very pretty object.  Caroline's Rose is just under the angular size of the Full Moon at 25 arc minutes diameter and is thought to lie around 8000 light years away from Earth.  This cluster is somewhat of an anomaly - it is very old (estimated to be 1.6 billion years old), but has not fully dispersed.  Its shape and dimensions do suggest something of a loose globular cluster, but this is not the case.  Whatever its origins and evolution, Caroline's Rose is a spectacular object in any binoculars or telescope and should be sought out by anyone with the optical means to do so.


Beyond Caph, following the line up from Shedar, we eventually come to the two last objects on our marathon around these constellations - M52 and the Bubble Nebula NGC 7635.  M52 is an open cluster found by Messier in 1774 and is +6.90 magnitude in brightness - easily seen in both binoculars and telescopes of all sizes.  Interior stars form a "V" which can be prominent to some observers, but better seen in astrophotographic images.  While M52 is an elegant cluster comprising of around 200 observable stars, there is some debate regarding its origins and distance.  Some sources put it  as close to us as 3900 light years, while others postulate a distance of 5000 light years.  Stellar population hints at an age of around 35 million years.


The Bubble nebula by Mark Blundell

More challenging from a visual perspective, but a perennial target for astrophotographers is the Bubble Nebula.  So-called because it has a quite evident bubble-like shell of gas suspended in front of a larger mass of nebulosity, the Bubble Nebula was discovered by William Herschel in 1787.  This nebula can be glimpsed in an 8-inch scope, but is much more impressive in a large 12-inch+ aperture instrument, especially when a UHC or OIII filter is used.  The bubble feature was caused by the sudden start of stellar wind from a new star born within the nebula's bounds.  The shock wave of this wind compressed the gas in front of it in all directions, forming a void and the bubble's surface and internal structure we see today.  While much of the Nebula is visible in large telecopies, the Bubble feature is largely the preserve of astrophotographers.  The nebula takes up 15 x 8 arc minutes  dimensions in the sky and is thought to be situated some 1400 light years away.      

Text: Kerin Smith