Page 87 - BBC Sky at Night Beginners Guide to Astronomy - 2017 UK

WHAT TO SEE

HOW TO

SEE AN

ECLIPSE

Three ways to see it

Left-right: The Moon
takes a small bite
out of the Sun; a
‘diamond ring’ effect
is observed; the total PINHOLE
eclipse; the ‘diamond A safe way of viewing an
ring’ appears again; and eclipse is with two pieces of
a fi nal, diminishing bite card. Make a small hole in one
and hold the other so that the
Sun is projected onto it. You can
then watch as events unfold.

seven minutes 31 seconds at
most, but you’ll probably see
a ‘totality’ lasting somewhere
between two and four minutes.
If you’re not within the 300km
circle of the shadow cone,
however, you’ll only see a
partial eclipse because the PROJECTING
makes the shadow of the Moon Moon covers up less of the You can set up binoculars on
passes above or below the Sun. cone-shaped (see ‘Casting Sun as you move further away a tripod to capture an eclipse.
Hold a piece of card away from
And because the Moon’s orbit shadows’, left). from the track of totality.
the eyepieces so the sunlight is
isn’t circular but elliptical, like This shadow cone starts out Do, however, be careful! projected onto it, then watch the
an oval, when it is furthest as big as the diameter of the Due to the intense light from Moon cover up the Sun.p he Sun.
from us and an eclipse occurs Moon at 3,476km (2,160 miles), the Sun, a total eclipse is
the Moon is too small to cover but by the time it reaches the dangerous to look at. The only
the Sun completely. We then Earth the shadow is much time when it’s safe to look
see an ‘annular eclipse’, in smaller – the biggest it can get directly at the eclipse is during
which a thin ring of sunlight is about 300km (190 miles) the few minutes of totality
can be seen circling the Moon. in diameter. If you’re lucky when the Moon completely
enough to be within the zone of covers the Sun. For the rest ECLIPSE GLASSES
SUN BLOCKED the shadow, you’ll see darkness of the event you must protect You can now buy safe eclipse
viewers that you wear just like
When we witness a total solar descend as the shadow sweeps your eyes from the Sun’s glare.
sunglasses. They cut out all
eclipse it means that we are in across the planet. Take appropriate care and you harmful ultraviolet and infrared
the shadow of the Moon and, as During an eclipse the Moon can fully enjoy this marvel of rays and 99.9 per cent of the
the Sun is the bigger object, it will cover the Sun entirely for celestial mechanics. Sun’s visible light.
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