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The Night Sky October 2006

Compiled by Ian Morison

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

Mk I

The Earth as seen from Saturn
Image: Cassini Imaging Team, SSL,JPL,ESA,NASA.

The Earth and Moon as seen from Saturn.

This wonderful new image was taken by the Cassini spacecraft in orbit around Saturn. The pale blue dot to the upper left of Saturn's rings is the Earth. The oceans give a bluish colouration to the Earth's reflection. Saturn was used to block the direct light from the Sun otherwise the Earth could not have been imaged. On the upper left is an expanded image of the Earth which shows a dim extension up to the right. This is the Moon.

The Moon

Third Quarter Moon old Moon
Third Quarter Moon - by Ian Morison using a 6" Maksutov-newtonian and Canon G6 camera.
new first quarter full moon last quarter
Oct 22nd Oct 29th Oct 6th Oct 13th

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

Highlights of the Month

A comet passes through Hercules below M13

Oct 27/28th: A comet passes below M13
Image: Stellarium/IM

Comet C/2006 M4 (SWAN) was discovered on June 20th 2006. It should reach its peak magnitude - estimated to be just below 6th magnitude - during the second half of October. During the nights of 27th, 28th and 30th it passes through Hercules just a few degrees below the globular cluster M13. M13 is a 6th magnitude globular cluster which will also look like a fuzzy object in binoculars! Given binoculars with low magnification (x7 or x8) it should be possible to see both M13 and the Comet in the same field of view.

Image: Carpal Tunnel

Seek out Uranus with binoculars or a telescope

This month: Uranus near to Lambda Aquarii.
Image: Stellarium/IM

October is another good month to observe the planet Uranus - perhaps for the first time - with binoculars, a small telescope or even your unaided eye! &nb &nbs On October 22nd, the night of new moon moon, Uranus, with a magnitude of 5.8, lies just 40 arc minutes below and to the right of the 4th magnitude star Lambda Aquarii. (If Lamdbda Aquarii is the centre of a clock, Uranus is at 4:30) During the month it drifts slowly westwards. Binoculars will easily show it and a small telescope will show a blue-green disc just under 4 arc seconds in angular diameter. Around the time of new moon (22nd October) under dark and transparent skies you even be able to see it with your unaided eyes. Have a go!

October 25:Jupiter, Mercury and the thin crescent Moon.

Image: Stellarium/IM

Just after sunset on the 25th October you will have a chance to see, Mercury and Jupiter just 4 degrees apart in the sky. The thin crescent Moon will be just to the left of them both - but you will need a low western horizon as they are at quite a low elevation when the Sun sets. Binoculars will help you pick them out. In fact, you will be able to see Jupiter and Mercury together for some days before and after the 25th.

Find the Andromeda Galaxy and observe Algol wink!

Mid evenings through October
Image: Stellarium/IM

The autumn is a good time to find the Andromeda galaxy. It is near the top of the chart just to the right of centre. Start at the top left star (Alpheratz) of the square of Pegasus, move round two bright stars to the left and up a bit to reach Mirach. At this point turn sharp right, move up one star and then the same distance again. A fainter star is passed and then you should see a fuzzy glow - that is the Nucleus of the Andromeda Galaxy. 10x50 binoculars on a really dark transparent night will show the disk extending out from the nucleus.

To the left of the tiny constellation Triangulum is the Star Algol in Perseus.

It is an eclipsing binary and every 2.87 days its brightness drops by more than a magnitude and then rises again. In October you can watch this happen over a period of hours around 22:25 UT on the 19th and 19:14 UT on the 22nd.

The Planets

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


A Cassini image of Jupiter . Nasa

Jupiter lying in the constellation Libra, is just visible low in the southwest after sunset at the beginning of the month see highlight above. As October starts it will be close to Alpha Librae - about 4 degrees away up and to the left. Due to its low elevation our views will be hindered by the atmosphere. It has a magnitude of ~ -1.8 and an angular size of 32.2 arc seconds. A chart on page 59 of Octobers's Sky and Telescope (S&T) shows where the four galillean satellites may be seen as they weave their way around it. A small telescope will usually show the Jupiter's equatorial bands but the low elevation will mean that the images will not be good. The image of Jupiter shown above was taken as the Cassini passed Jupiter on its way to Saturn. It is the highest resolution view of Jupiter ever taken.


The planet Saturn. Cassini - Nasa

Saturn is in the constellation Leo and about 8 degrees up and to the right of its brightest star Regulus. It passed behind the Sun on August 7th and, by the beginning of October it rises at ~3:00 BST, but is best seen in the east north-east before dawn. By the end of October it will rise about midnight UT. Its magnitude will then be ~ +0.5 and its globe will subtend an angle of 17.6 arc seconds. The rings are closing and are now about 15 degrees from edge-on, so Saturn will shine less brightly than during the previous eight years when the rings have been more open. Saturn is still a beautiful sight in a small telescope. A 4 to 6 inch telescope will also easily show Saturn's largest moon Titan, and an 8 inch three or four more.

The image was taken as the Cassini spacecraft neared Saturn at the start of its exploration of the planet and its moons - particularly Titan.


Mariner 10 composite image of Mercury. Nasa

Mercury reaches its greatest elongation from the Sun on October 16th. But it will set only 45 minutes after the Sun so will still be very difficult to see. On the 25th and 28th of October it is in conjunction with Jupiter (both having the same Right Ascension) see highlight above. Sadly due to their very low elevations they will not be easy to pick out.

Note that the blank region in the image above is simply because this part of Mercury's surface has not yet been imaged in detail.


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

Mars is now passing behind the Sun (conjunction is on October 23rd) and we will have to wait until it reappears in the pre-dawn sky in a few months.


Venus showing some cloud structure

Venus passes behind the Sun on October 27th so is barely visible this month. In the first week of October it might just be glimpsed above the eastern horizon before dawn - but you will be better rewarded by observing Saturn!

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 October Sky

October Sky
The October Sky in the south - mid evening

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 with Perseus below.

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