Page 15 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

NEED TO KNOW
You’re observing; your eyes are torch adapted with red paper, red is not too bright, as that will ruin
dark-adapted, and yet you’d still cellophane sweet wrappers or red your dark adaption: all you need
RED like to see charts and be sure paint over the front. Dark-adapted is enough light to see by. You can
that you’re not about to step on eyes are much less sensitive to red also buy purpose-made red light
TORCHES a hedgehog. The answer is a light. Just make sure the red light torches, so no DIY is required.

On page 6, we introduced our fi rst group of stars, Just to clear up any confusion at this point, the
the Plough, and mentioned how useful it was for Plough is not a constellation: technically, it is what’s HOPPING
fi nding the other stars and constellations around called an asterism. This simply means that it is a WITH
the starry skies. Indeed, you could call the Plough a group of stars that are easily recognisable. The BINOCULARS
signpost to the stars. actual constellation to which the Plough belongs is
Binoculars provide
However, before we actually cast off and stargaze Ursa Major, the Great Bear. Our saucepan friend
another way to star-
further afi eld, there are a few things to look at in creates the back and tail of the Bear. hop. The trouble is,
the Plough itself. Many constellations look nothing like the when you look through
Firstly, it’s worth noting that each of the animal, person or object they are supposed to them it’s easy to lose
Plough’s seven stars has its own name. Notice represent, but Ursa Major is actually one of the your bearings because
you’re only looking at a
where the star Mizar is – it’s located right at the exceptions. Mind you, you still need a fair amount
small piece of sky. So
‘bend’ in the Plough’s handle. This star, together of imagination! So next time you’re out, have a go at
it’s useful to work out
with a companion that’s not quite as bright, forms the joining the dots on the Great Bear. how much of the sky
a well-known double star that is visible to the Anyway, back to Dubhe. The best way of seeing your binoculars show
unaided eye. Apparently, at some stage it was used its orangey-yellow hue is to compare it with the star you (their fi eld of view).
to test whether you had good eyesight, although below it in the Plough: the pure white Merak. If you To do this, take a
how reliable that test really could have been is fl ip your sight between these two, then the orangey- look at the Plough,
noting which stars are
debatable, as Mizar’s companion is not a very faint yellow colour of Dubhe should be apparent.
at the very edge of
star, and you can see it quite easily. the view through your
So what exactly are you looking for? Well, with POINTING THE WAY binoculars. Now fi nd
the Plough in its usual orientation as a saucepan Now that you know where Dubhe and Merak are, these stars on a star
sitting fl at on a cooker, take a look to the top-left you’ve just met two of the most useful stars in chart and make a ring
of Mizar at a distance of about one-third of the the night sky. These two stars are known as the out of wire and place it
around them. This ring
diameter of the Moon – that’s about one-third of the Pointers, because they can be extremely useful
is the fi eld of view of
width of your little fi nger. when it comes to locating other stars. your binoculars
There, with any luck, will be Mizar’s companion: Starting with Merak, draw an imaginary line at the right
a star named Alcor. This is the fi rst of many double through Dubhe and keep going. The next star scale to use on
stars that we’ll fi nd. of any note you come across is the very famous your star chart.
Polaris (also known as the Pole Star) or North Star. You can then
BELONGING TO THE BEAR Don’t expect this to be a super-bright example of move your wire
ring around the
Both Mizar and its companion Alcor are white stellar marvellousness – it isn’t. Polaris is just an chart to plan
stars, but on the other side of the Plough is our ordinary-looking star. It’s famous because it sits each step of
fi rst coloured star. The top-right star of the main almost directly above Earth’s North Pole, so as we your star-hop
‘saucepan’ part has a slight orangey-yellow hue. spin, this star appears to stay practically in the and know what
This star is called Dubhe. It is the brightest star in same place. the view should
look like. Try
the Plough, and indeed it is also the leading star And that’s just the start – the Plough can help
aiming for the
of the constellation to which the Plough belongs. you fi nd many more stars and constellations.
Double Cluster
in Perseus – it’s
a great target through
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❯ REGULUS AND LEO ❯ CAPELLA AND AURIGA TURN THE
To get to Leo, the Lion, you also start from Megrez, To fi nd Auriga, the Charioteer, start again from PAGE FOR
but this time trace a line through Phecda, below it Megrez, but this time take a route through Dubhe, to MORE
in the Plough. Continuing on this line you travel to its right. After an expanse of emptiness that includes
Regulus, the leading star in Leo. The head of the Lion the very faint constellation of Camelopardalis, TARGETS
is made by an easily seen sickle-shaped asterism of the Giraffe, you will eventually arrive at the bright
stars that works up from Regulus. yellow star Capella, the lead star of Auriga.
skyatnightmagazine.com 2012 15