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Skywatch October

October is a feast of opportunity for those early risers wanting to view the planets.  

Get up before dawn on a cool, clear morning and you’ll see Venus as a brilliant object, visible in the eastern sky for several hours before sunrise.

Whilst pointing a telescope at it shows no apparent detail, you can spot the crescent phase in the early part of the month with a high power.  The phase of Venus works in the same way as the phases of our Moon – from crescent to full to crescent again as Venus orbits the Sun. As the month progresses, the phase will increase to about half.

Jupiter continues as a magnificent morning object in the eastern sky.  For October, Jupiter is situated in the constellation of Leo the Lion, so when you spot Jupiter, just look a little above and you are into Leo; to the west of Jupiter lies the sickle of Leo, a question mark shape that symbolises the Lion’s mane.

If that isn’t enough, Mars is also rising at around the same time.  It’s easy to locate as the planet lies close to Venus and Jupiter.  On the morning of 17th October, Mars will lie only half a degree (one Moon diameter) north of Jupiter.

Little Mercury also returns to the dawn skies from around 8th October.  Look east-south-east from then until around 5th November when it descends below the horizon.

With the planets in the same area of the sky this month, it is a good time to see planetary conjunctions, a term used to describe two or more planets visually close together within 1 degree in the sky.   You can measure 1 degree by holding your hand at arm’s length – 1 degree is the width of your little finger.

On the 26th at around 5:00am, Venus, and Jupiter rise in conjunction in the eastern sky, and on the 28th Mars joins the group in a rare “three planet” conjunction.  They take on the shape of a tight triangle so this is a sight well worth getting up early for.


Following Pegasus in the autumn sky comes Perseus, the Greek hero who rescued Andromeda.  His constellation contains the loveliest pair of star clusters in the northern hemisphere known as the Double Cluster.  From a dark site, you can spot them with the naked eye, but use your binoculars or a small telescope and you can see a glittering collection of stars.  These clusters lie some 7,600 light years away and are 13 million years old; quite how they formed is still a mystery.  To find the Double Cluster, follow the characteristic curve of Perseus, then from Mirfak, keep the curved line going and you will encounter the Double Cluster.

Perseus also has two other objects to see; Algol, known as the “Demon Star” is a variable star that changes its brightness every 3 days.  Its light dims and brightens due, it is thought, to a companion star in orbit around it. Close to Algol is Messier (M) 34, an open cluster of stars easily spotted in binoculars.  An open cluster is a group of young stars which are beginning their journey out into our galaxy. Open clusters contain from a few tens of stars to a few thousand; M34 contains around 100 stars.


Our autumn season starts again on Wednesday 7th October.  We meet inside The Red Lion at Kilmington from 8.00 to 8.30pm.  Old hands and beginners equally welcome, just turn up on the night, with or without a telescope.  We observe from White Sheet Hill afterwards. The November meeting will be on Wednesday 4th.  Details are on our website at

Article supplied by Mendip & Dorset Viewers –