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September astronomy highlights

September's Highlights

The summer triangle is now heading westward earlier each night and the constellations of autumn swing into view...

Among these Autumnal groupings are Pegasus, Andromeda and Cassiopeia. The easily recognisable 'W' shape of Cassiopeia sits in the arc of the Milky Way, that faint band of light which is a spiral arm of our own galaxy. It stretches east-west on autumn evenings and is wonderful to scan with binoculars or a small telescope.

The planet Uranus reaches opposition this month. You will need at least binoculars to see it and I will give you some tips later on how to find it.

The planet Venus passes close to the 'Beehive' cluster this month.

As the Sun heads towards its peak of activity next year there is the likelihood of more sunspots to see on its surface, with the proper filters of course, and also the likely increase of auroral activity. September skies are often dark enough to start observing this phenomenon at the start of the season. If you live in northern parts of the UK or Europe then your chances of seeing the Aurora increase dramatically, but with solar activity high, your chances of seeing the Northern Lights also increases further south. If you have never seen the Aurora Borealis before, it is a magnificent sight, but you will need dark clear skies to see it at its best advantage. I will be posting some information and images on my blog soon all about the Aurora. www.astronomyknowhow.com/blog

The Planets This Month

There are two planetary highlights this month, one being literally more obvious than the other...

Firstly Jupiter is now showing well in our skies after its reappearance from behind the Sun from our point of view. Since its emergence, it has been seen to have a lot of turbulence in its cloud belts and the 'Great Red Spot' has been quite pale in colour. So if you have a telescope it is well worth keeping an eye on the king of the planets to see what might happen next.

Mercury will change from a morning 'star' to an evening one during September. The best time to see it will be on the 1st where it will be a little over 1-degree to the north of the star Regulus in Leo at about 5:30am BST. Be careful if you are using binoculars to view Mercury as the Sun will be close to rising at this time.

Saturn and Mars have all but disappeared into the evening twilight but Uranus and Neptune are well placed for viewing. Neptune is now just past opposition and is visible all night, but you will need at least binoculars in order to find it. It lies in the constellation of Aquarius due south around midnight.

Uranus reaches opposition this month (directly opposite the Sun in the sky from our point of view) in the constellation of Pisces. Opposition is on the 29th and it will be visible all night although the best time to see it will around 1:00am BST due south on this particular evening. In binoculars, but especially with the extra magnification of a small telescope, it will appear as a tiny greenish coloured disc. It is fairly featureless. The real fun of finding this planet is the fact that it is so far away. Uranus lies over 2.5 billion kilometres from Earth!

Venus is still incredibly bright in the pre-dawn sky all through the month. The amount of its disc which is illuminated increases steadily throughout the month to as much as 70% at the end of September. The best time to view this planet is in the early hours around 4:00am BST and the mornings of the 12th and 13th are to be particularly recommended due to its close proximity to the Beehive Cluster.

Venus and the Beehive

Although the title to this sounds a little like an ancient Greek myth, what it is really about is a spectacular encounter of the planet with a lovely deep-sky object known as the 'Beehive Cluster' or M44.

Venus will be at its closest to this star cluster on the mornings of the 12th and 13th September although it will still remain fairly close for several days either side of these dates.

The Beehive Cluster lies in the constellation of Cancer the Crab and when viewed through binoculars it is easy to see why it has been given this name.

This event through binoculars or a low power eyepiece in a small telescope will look stunning. Nearby to the west of Venus on the 12th will be a thin crescent Moon which will be below to the south of the planet on the 13th, which will add to the charm of the scene. The best time to catch it will be 4:00am (sorry!) and let's hope for clear skies. If you plan to try photographing it, you may find it quite tricky as Venus will be incredibly bright compared to the cluster. Take lots of exposures of varying lengths and at varying apertures to see which looks best.

Deep Sky Highlights of September

The constellations of autumn are now moving into view and bringing with them some stunning sights...

Due south-east around midnight in the middle of the month the large constellation of Pegasus the winged horse will be very noticeable and easily recognisable by the four stars which make up the 'square' of Pegasus. The star at the top left hand of the 'square', if you are in the northern hemisphere, in fact belongs to another constellation, that of Andromeda. This constellation is of course famous for playing host to the galaxy of the same name. The Andromeda Galaxy or M31 is the largest and brightest visible from the northern-hemisphere and is best seen in binoculars. Very close to it are its two satellite galaxies of M32 and M110. This is a fantastic area to explore with binoculars or a small telescope with a low power eyepiece.

If you head south-east from the Andromeda Galaxy across the constellation you will come to the much harder to see M33 'Triangulum Galaxy'. This is nearly as large as its neighbour but has a lower surface brightness and is face on to us, so we can see the spiral structure quite plainly. Again this is quite an extensive object and best seen in binoculars from a dark sky site.

If you draw an imaginary line from M33 back to M31 and keep going around twice this distance you will find yourself in the fairly faint constellation of Lacerta the Lizard. This is only a relatively small constellation but does contain the pretty open cluster NGC 7243 which is embedded in the Milky Way and shows up well in binoculars.

Head north again and you'll come to the constellation of Cepheus 'The King' who was husband of Queen Cassiopeia. The constellation looks a little like a child's drawing of a house with a very pointed roof. Just under the line joining the two stars at the bottom of the 'house', is a beautiful red coloured stars known as Herschel's Garnet Star or Mu Cephei. Do take the trouble to find this star as it is a lovely sight in binoculars or a telescope and is simply huge, being around 1000 times larger than our Sun. It is thought to be around 100,000 times brighter too!

Next head eastward and you will be among the stars of Cassiopeia, instantly recognisable from it loose 'w' pattern of bright stars. Lying in the Milky Way, this region of sky is packed with lovely star clusters and nebulosity. Just scan through it with you binoculars or telescope, you are sure to find many wonderful objects to catch your eye.

As you can see the early autumn skies are full of delights for the deep-sky observer. All you need to do is to go and look.