Star-hopping guide: find your way around the skies

If you’re starting out in astronomy, then our star-hopping tutorial is the best method of learning your way around the heavens.

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Image Credit: 
Jon Hicks

To some people these days, the idea of star-hopping seems rather quaint. The idea that you slowly work your way around the sky using only your eyes to identify star after star, steadily building up the patterns of the constellations, surely belongs to a bygone age.

After all, today we have Go-To telescopes that can take you to any star or fuzzy nebula instantly. There you go – no knowledge of the sky necessary. Go-To telescopes certainly have their place.

For example, if you want to show the wonders of the night sky to a group of friends, it’s just a case of pressing some buttons and hey presto: deep-sky object after deep-sky object appears as if by magic. Certainly, with their computer databases of where each galaxy and nebula is located, Go-To telescopes are great for finding some of the more challenging, faint, fuzzy blobs.

However, there is something very rewarding in having a mental map of the stars, so that you can glance up with confidence and point out Leo, Gemini or Ursa Major to whoever is within earshot. And that’s before you’ve pointed out the planets, which are sure to increase anyone’s fascination in the night sky.

It’s true to say that few people know their way around the night sky well enough. The only way of being able to gain this useful and entertaining knowledge is to learn the sky – and it is by star-hopping that you learn.

A Universe to discover

Star-hopping really is fascinating. Not only are you recognising the patterns of constellations, you’re also learning about star distances, star colours, ages and names.

You’ll find that the whole of the night sky is an amazing mixture of space, time, history, science and world cultures. It’ll lead you off on all sorts of paths and you’ll learn things that will amaze others. Not to mention the basic reason – you’ll know what you’re looking at.

Now, you don’t need any optical instruments to begin star-hopping, but it does help to have a few things handy to make your evenings more enjoyable.

Firstly, let’s deal with the comfort aspect. Even in the summer, it will probably get chilly – at the very least – so wrap up warm. Then, to get as comfortable as possible, set up a deck chair or sun-lounger – maybe we should call it a star-lounger in this case.

Just before you pop outside to try some real star-hopping, there are a couple of final useful things to have with you: a star chart or atlas, plus a red torch to see the charts, and also where you’re going, without ruining your night vision. And don’t forget a flask of tea and a few biscuits for when you fancy a break.

If you’re new to star-hopping, position your star-lounger north-south and sit with your feet pointing north. This will put you in an ideal position to see several key star-hopping points: the Plough, the North Star and the constellation of Cassiopeia as they’re all around the north part of the sky.

Why not practise star-hopping using the example shown below? Remember, take it easy, and you’ll be finding your way around the sky in no time.

Star-hop from the Plough to Cassiopeia

1 Find the Plough

The Plough is a shape or ‘asterism’ found in the constellation of Ursa Major, the Great Bear. It’s a good place to start because it’s a recognisable shape. It’s also close to the north pole of the sky, meaning it’s always visible in the night sky.

2 Move from the Plough to the Pole Star

The two right-hand stars of the Plough are known as the Pointers. Extend an imaginary line between them and out of the Plough and they’ll point to the Pole Star, which is also called Polaris.

3 Trace the shape of Ursa Minor

The Pole Star is the main star of the constellation Ursa Minor, the Little Bear. This is shaped like a smaller, fainter version of the Plough and you can trace its form arching off from Polaris. Well done, you’ve found a new constellation.

4 Move on to Cassiopeia

Continue on in the same direction you took from the Plough to Polaris, for around the same distance again. You’ll find the distinctive ‘W’ of stars that make up the constellation of Cassiopeia. That’s it, a successful star-hopping session.

Hopping with binoculars

Binoculars provide another way to star-hop. The trouble is, when you look through them it’s easy to lose your bearings because you’re only looking at a small piece of sky. A good trick is to work out how much of the sky your binoculars show you (their field of view).

To do this, take a look at the Plough, noting which stars are at the very edge of your binoculars’ field of view. Now find these stars on a starchart and make a ring out of wire and place it around them.

This ring is the field of view of your binoculars at the right scale to use on your starchart.

You can then move your wire ring around the chart to plan each step of your star-hop and know in advance what the view should look like.

Try aiming for the Double Cluster in Perseus – it’s a great target through binoculars and it’s very close to Cassiopeia.

This article appeared in the September 2008 issue of BBC Sky at Night Magazine

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