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The Night Sky September 2012

Compiled by Ian Morison

Try and spot Uranus

This page, updated monthly, will let you know some of the things that you can look out for in the night sky.  It lists the phases of the Moon, where you will see the naked-eye planets and describes some of the prominent constellations in the night sky during the month.

Image of the Month

Gale crater

Mars Curiosity views its landing site


How could one not choose an image taken by the Mars Curiosity Rover? This image shows the floor of the Gale crater in which Curiosity landed (in such spectacular fashion) and across to the distant crater wall.   The foreground has the appearance of a dried river bed.

Highlights of the Month

September around 9pm: Spot Brochi's Cluster and the double star Albireo in Cygnus.

Brochis's Cluster
Brochi's Cluster - The Coathanger and Albireo
Image: Stellarium/IM
By about 10 pm during the month as darkness falls, the constellations Cygnus, Lyra and Aquila will have risen well up into the south-east.   Their three brightest stars Deneb, Vega and Altair respectivly make up the "Summer Triangle".   If you sweep with binoculars one third of the way from Altair towards Vega, you should spot Brocchi's Cluster - usually called "The Coathanger" as this is exactly what it looks like, but seen upside down.   Its not thought to be a real cluster but an "asterism" which is a chance grouping of stars.   Not far to the upper left of Brochi's cluster is, perhaps, the most beautiful double star to observe in a small telescope.   It is the star Albireo which forms the head of the swan.   At magnitude 3 it is the least brightest of the stars that make up a part of Cygnus called the "Northern Cross".   However, when seen through a small telescope, it is seen to be made up of two stars showing a beautiful colour contrast.   The brighter 3.1 magnitude component (which is itself a double star) is amber in colour whilst the 5.1 magnitude companion star is blue-green in colour.   With a separation of 35 arc seconds the pair can be easily split even under poor seeing conditions.

September 8th before dawn: Jupiter and the third quarter Moon

Jupiter and Moon
Jupiter close to a third quarter Moon.

Before dawn on the morning of the 8th September Jupiter lies in Taurus close to the Moon at third quarter.

September 19th after sunset: Mars, Saturn and a thin crescent Moon

Mars, Saturn and a thin crescent Moon
Mars, Saturn and a thin crescent Moon

Given a clear sky and a good low western horizon on the 19th of September, Mars (magnitude +1.2) will be seen just up to the left of a thin crescent Moon with Saturn (magnitude +0.8) appearing over to their right.

Around September 21st: Spot Uranus - appearing as a double star!

Find Uranus in Pisces: Stellarium/IM.

The planet Uranus is closest to the Earth on the 29th, so September is very good time to look for it!   Around New Moon on the 12th-19th Septemeber will be best as the skies will be darkest - but there is a good reason to observe it closer to the 21st.   The two diagrams show you where it lies in the constellation Pisces - not the easiest to find this year!   At magnitude 5.7, you should be able to spot it with binoculars and a telescope should even show a turquoise disk just 3.7 arc seconds across.   This is where a "GOTO" mount can be quite useful!   But this year there is a bonus!   Uranus is passing very close to the star 44 Piscium which has an almost identical magnitude so the pair will look like a double star for a few days around the 21st - 25th.   Their closest approach or "appulse" brings them to within 0.7 arc minutes - but happens at midday on the 23rd so we will not be able to observe it.   (No, I have never come across that word either!)

Detailed star chart: Stellarium/IM

September 30th: Venus close to Regulus in Leo

Venus in Leo
Venus in Leo close to Regulus
Image: Stellarium/IM

Before dawn on the 30th Venus will lie in Leo, just 3 degrees to the upper right of Regulus, Alpha Leonis.

September: 6/7th and 23/24th: The Alpine Valley

Alpine Valley
Alpine Valley region

An interesting valley on the Moon: The Alpine Valley
These are good nights to observe an interesting feature on the Moon if you have a small telescope.  Close to the limb is the Appenine mountain chain that marks the edge of Mare Imbrium.  Towards the upper end you should see the cleft across them called the Alpine valley.   It is about 7 miles wide and 79 miles long.   As shown in the image a thin rill runs along its length which is quite a challenge to observe.  Over the next two nights following the 3rd/4th the dark crater Plato and the young crater Copernicus will come into view.   This is a very interesting region of the Moon!

[Note: you might wonder how the above dates were found.   There is a excellent free program called "Virtual Moon Atlas" which allows one to see what will be visible on any night - one then simply finds when the terminator will be close to the object of interest.]
The Alpine Valley
The Alpine valley and the crater Plato

A Messier Object imaged with the Faulkes Telescope: M82 in Ursar Major

Galaxy M82
Image:Danial Duggan
Faulkes Telescope North.

Galaxy M82, imaged by Daniel Duggan.
This image was taken using the Faulkes Telescope North by Danial Duggan - for some time a member of the Faulkes telescope team.   Lying at at distance of 12 million light years in the constellation Ursa Major, it makes a pair with M81.   Tidal interactions between them have initiated a "burst" of star formation hence it is called a "starburst" galaxy.   At its heart, one star becomes a supernova every 30 years or so and their evolution is being studied by radio telescopes such as the Jodrell Bank MERLIN array and the European VLBI network that can image the expanding shell of gas resulting from the stellar explosions.

Learn more about the Faulkes Telescopes and how schools can use them: Faulkes Telescope"

Observe the International Space Station

The International Space Station
The International Space Station and Jules Verne passing behind the Lovell Telescope on April 1st 2008.
Image by Andrew Greenwood

Use the link below to find when the space station will be visible in the next few days. In general, the space station can be seen either in the hour or so before dawn or the hour or so after sunset - this is because it is dark and yet the Sun is not too far below the horizon so that it can light up the space station. As the orbit only just gets up the the latitude of the UK it will usually be seen to the south, and is only visible for a minute or so at each sighting. Note that as it is in low-earth orbit the sighting details vary quite considerably across the UK. The NASA website linked to below gives details for several cities in the UK. (Across the world too for foreign visitors to this web page.)

Note: I observed the ISS three times recently and was amazed as to how bright it has become.

Find details of sighting possibilities from your location from: Location Index

See where the space station is now: Current Position

The Moon

3rd Quarter Moon
The Moon at 3rd Quarter. Image, by Ian Morison, taken with a 150mm Maksutov-Newtonian and Canon G7.
Just below the crator Plato seen near the top of the image is the mountain "Mons Piton".   It casts a long shadow across the maria from which one can calculate its height - about 6800ft or 2250m.
new moon first quarter full moon last quarter
September 16th September 22nd September 30th September 8th

Some Lunar Images by Ian Morison, Jodrell Bank Observatory: Lunar Images

A World Record Lunar Image

World record Lunar Image
The 9 day old Moon.

To mark International Year of Astronomy, a team of British astronomers have made the largest lunar image in history and gained a place in the Guinness Book of Records! The whole image comprises 87.4 megapixels with a Moon diameter of 9550 pixels. This allows details as small as 1km across to be discerned! The superb quality of the image is shown by the detail below of Plato and the Alpine Valley. Craterlets are seen on the floor of Plato and the rille along the centre of the Alpine valley is clearly visible. The image quality is staggering! The team of Damian Peach, Pete lawrence, Dave Tyler, Bruce Kingsley, Nick Smith, Nick Howes, Trevor Little, David Mason, Mark and Lee Irvine with technical support from Ninian Boyle captured the video sequences from which 288 individual mozaic panes were produced. These were then stitched together to form the lunar image.

Plato and the Alpine valley
Plato and the Alpine Valley.

Please follow the link to the Lunar World Record website and it would be really great if you could donate to Sir Patrick Moore's chosen charity to either download a full resolution image or purchase a print.

The Planets

 A montage of the Solar System
A montage of the Solar System. JPL / Nasa


A Cassini image of Jupiter . Nasa

Jupiter rises around midnight at the beginning of September and at 10 pm by month's end but will be best seen before dawn some 60 degrees above the horizon in the constellation of Taurus, the Bull.   Shining at magnitude -2.3 it starts September lying just ~6.5 degrees to the upper left of the star Aldebaran, the eye of the Bull.   It is gradually moving towards the Bull's horns and increases its magnitude to -2.5.   Over the month its angular diameter increases from 39 to 43 arc seconds so even a small telescope will show plenty of detail with the bright zones and darker bands crossing the disk and up to four Gallilean moons visible.

See highlight above.


The planet Saturn. Cassini - Nasa

Saturn, is now close to the end of its apparition and, as September begins, is seen low in the west after sunset shining at magnitude +0.8.   It the lies in Virgo just 5 degrees north of the first magnitude star Spica, Alpha Virginis, and is moving slowly eastwards to end the month 7 degrees away.   Its disk is ~16 arc seconds across and the rings are ~14 degrees from the line of sight in mid September and span some 36 arc seconds.   With a small telescope, Saturn's largest satellite, Titan, can be easily seen.

See highlight above.


Messenger image of Mercury Nasa

Mercury, really lies too close to the Sun to be visible this month.


Mars showing Syrtis major.
A Hubble Space Telescope image of Mars.
Jim Bell et al. AURA / STScI / Nasa

Mars, moving eastwards through Virgo and Libra is now, sadly, well past its best and reaching the end of its apparition, visible low in the west after sunset.   It starts the month in Virgo, 10 degrees to the left of Saturn but soon moves into Libra. Its magnitude remains at +1.2 during the month whilst its angular diameter falls from 5.2 to 4.8 arc seconds so it is unlikly that any surface marking could be seen on its salmon-pink disk.   On the 1st of the month, its elevation is only ~8 degrees as darkness falls and this reduces as the month progresses.

See highlight above.


Venus showing some cloud structure

Venus. rises about 3 hours before the Sun this month and, with a magnitude of -4.2 dominates the pre-dawn sky.   It is moving rapidly eastwards, starting the month in Gemini, crossing into Cancer on the 4th and into Leo on the 23rd, ending the month just 3.5 degrees up to the right of Regulus.   During September, its angular size drops from 20 to 16 arc seconds but, at the same time, the percentage illumination increases from 58 to 70% so the brightness hardly changes - from -4.3 to -4.1 magnitudes.

See highlights above.

Radar Image of Venus
Radar image showing surface features

Find more planetary images and details about the Solar System: The Solar System

The Stars

The Evening September Sky

September Sky
The September Sky in the south - early Sept:~11pm, late Sept:~10pm

This map shows the constellations seen towards the south in late evening. To the south in early evening moving over to the west as the night progresses is the beautiful region of the Milky Way containing both Cygnus and Lyra. Below is Aquilla. The three bright stars Deneb (in Cygnus), Vega (in Lyra) and Altair (in Aquila) make up the "Summer Triangle". East of Cygnus is the great square of Pegasus - adjacent to Andromeda in which lies M31, the Andromeda Nebula. To the north lies "w" shaped Cassiopeia and Perseus.

The constellations Lyra and Cygnus

Cygnus and Lyra
Lyra and Cygnus

This month the constellations Lyra and Cygnus are seen almost overhead as darkness falls with their bright stars Vega, in Lyra, and Deneb, in Cygnus, making up the "summer triangle" of bright stars with Altair in the constellation Aquila below. (see sky chart above)


Lyra is dominated by its brightest star Vega, the fifth brightest star in the sky. It is a blue-white star having a magnitude of 0.03, and lies 26 light years away. It weighs three times more than the Sun and is about 50 times brighter. It is thus burning up its nuclear fuel at a greater rate than the Sun and so will shine for a correspondingly shorter time. Vega is much younger than the Sun, perhaps only a few hundred million years old, and is surrounded by a cold,dark disc of dust in which an embryonic solar system is being formed!

There is a lovely double star called Epsilon Lyrae up and to the left of Vega. A pair of binoculars will show them up easily - you might even see them both with your unaided eye. In fact a telescope, provided the atmosphere is calm, shows that each of the two stars that you can see is a double star as well so it is called the double double!

The Double Double
Epsilon Lyra - The Double Double

Between Beta and Gamma Lyra lies a beautiful object called the Ring Nebula. It is the 57th object in the Messier Catalogue and so is also called M57. Such objects are called planetary nebulae as in a telescope they show a disc, rather like a planet. But in fact they are the remnants of stars, similar to our Sun, that have come to the end of their life and have blown off a shell of dust and gas around them. The Ring Nebula looks like a greenish smoke ring in a small telescope, but is not as impressive as it is shown in photographs in which you can also see the faint central "white dwarf" star which is the core of the original star which has collapsed down to about the size of the Earth. Still very hot this shines with a blue-white colour, but is cooling down and will eventually become dark and invisible - a "black dwarf"! Do click on the image below to see the large version - its wonderful!

M57 - The Ring Nebula
M57 - the Ring Nebula
Image: Hubble Space telescope

M56 is an 8th magnitude Globular Cluster visible in binoculars roughly half way between Alberio (the head of the Swan) and Gamma Lyrae. It is 33,000 light years away and has a diameter of about 60 light years. It was first seen by Charles Messier in 1779 and became the 56th entry into his catalogue.

M56 - Globular Cluster
M56 - Globular Cluster


Cygnus, the Swan, is sometimes called the "Northern Cross" as it has a distinctive cross shape, but we normally think of it as a flying Swan. Deneb,the arabic word for "tail", is a 1.3 magnitude star which marks the tail of the swan. It is nearly 2000 light years away and appears so bright only because it gives out around 80,000 times as much light as our Sun. In fact if Deneb where as close as the brightest star in the northern sky, Sirius, it would appear as brilliant as the half moon and the sky would never be really dark when it was above the horizon!

The star, Albireo, which marks the head of the Swan is much fainter, but a beautiful sight in a small telescope. This shows that Albireo is made of two stars, amber and blue-green, which provide a wonderful colour contrast. With magnitudes 3.1 and 5.1 they are regarded as the most beautiful double star that can be seen in the sky.

Alberio: Diagram showing the colours and relative brightnesses

Cygnus lies along the line of the Milky Way, the disk of our own Galaxy, and provides a wealth of stars and clusters to observe. Just to the left of the line joining Deneb and Sadr, the star at the centre of the outstretched wings, you may, under very clear dark skys, see a region which is darker than the surroundings. This is called the Cygnus Rift and is caused by the obscuration of light from distant stars by a lane of dust in our local spiral arm. the dust comes from elements such as carbon which have been built up in stars and ejected into space in explosions that give rise to objects such as the planetary nebula M57 described above.

There is a beautiful region of nebulosity up and to the left of Deneb which is visible with binoculars in a very dark and clear sky. Photographs show an outline that looks like North America - hence its name the North America Nebula. Just to its right is a less bright region that looks like a Pelican, with a long beak and dark eye, so not surprisingly this is called the Pelican Nebula. The photograph below shows them well.

The North American Nebula
The North American Nebula

Brocchi's Cluster An easy object to spot with binoculars in Gygnus is "Brocchi's Cluster", often called "The Coathanger",although it appears upside down in the sky! Follow down the neck of the swan to the star Alberio, then sweep down and to its lower left. You should easily spot it against the dark dust lane behind.

The Coathanger
Brocchi's Cluster - The Coathanger

The constellations Pegasus and Andromeda

Pegasus and Andromeda
Pegasus and Andromeda


The Square of Pegasus is in the south during the evening and forms the body of the winged horse. The square is marked by 4 stars of 2nd and 3rd magnitude, with the top left hand one actually forming part of the constellation Andromeda. The sides of the square are almost 15 degrees across, about the width of a clentched fist, but it contains few stars visibe to the naked eye. If you can see 5 then you know that the sky is both dark and transparent! Three stars drop down to the right of the bottom right hand corner of the square marked by Alpha Pegasi, Markab. A brighter star Epsilon Pegasi is then a little up to the right, at 2nd magnitude the brightest star in this part of the sky. A little further up and to the right is the Globular Cluster M15. It is just too faint to be seen with the naked eye, but binoculars show it clearly as a fuzzy patch of light just to the right of a 6th magnitude star.


The stars of Andromeda arc up and to the left of the top left star of the square, Sirra or Alpha Andromedae. The most dramatic object in this constellation is M31, the Andromeda Nebula. It is a great spiral galaxy, similar to, but somewhat larger than, our galaxy and lies about 2.5 million light years from us. It can be seen with the naked eye as a faint elliptical glow as long as the sky is reasonably clear and dark. Move up and to the left two stars from Sirra, these are Pi amd Mu Andromedae. Then move your view through a rightangle to the right of Mu by about one field of view of a pair of binoculars and you should be able to see it easily. M31 contains about twice as many stars as our own galaxy, the Milky Way, and together they are the two largest members of our own Local Group of about 3 dozen galaxies.

M 31 - The Andromeda Nebula
M31 - The Andromeda Nebula

M33 in Triangulum

If, using something like 8 by 40 binoculars, you have seen M31 as described above, it might well be worth searching for M33 in Triangulum. Triangulum is

the small faint constellation just below Andromeda. Start on M31, drop down to Mu Andromedae and keep on going in the same direction by the same distance as you have moved from M31 to Mu Andromedae. Under excellent seeing conditions (ie., very dark and clear skies) you should be able to see what looks like a little piece of tissue paper stuck on the sky or a faint cloud. It appears to have uniform brightness and shows no structure. The shape is irregular in outline - by no means oval in shape and covers an area about twice the size of the Moon. It is said that it is just visible to the unaided eye, so it the most distant object in the Universe that the eye can see. The distance is now thought to be 3.0 Million light years - just greater than that of M31.

M33 in triangulum - David Malin