What is a Lunar Eclipse?
A total lunar eclipse occurs when the Earth comes between the Sun and the Moon and covers the Moon with its shadow. When this happens the Moon can turn red, hence the nickname blood moon.
The red colour is caused by light scattering as the Sun's rays pass through the Earths atmosphere. The process is called Rayleigh scattering and it bends red light from the sun like a lens into the space behind Earth. This is also why sunset and sunrise are red and orange in colour.
- Umbra: The darker, central part of the Earth's shadow
- Penumbra: The lighter, outer part of the shadow cast by our planet
Why will the eclipse last so long?
There are a couple of reasons for why the eclipse will last so long.
The eclipse is happening at the same time as the moon's apogee - when it's at its furthest point away from Earth, so the Moon is the smallest apparent size it can be. Secondly, it will be passing directly into the darkest region of the Earth's shadow where it is at its widest point. These two factors make for the longest possible eclipse.
Viewing the Lunar Eclipse
Where skies are clear of cloud, the spectacle will be visible almost everywhere around the world, with the exception of North America. The eclipse will already have started by the time the Moon rises over the UK and Western Europe.
From the UK and Europe, the South-east will be the place to look for the rising, eclipsing Moon with bright red Mars below. As the moon rises at 8:50 pm, the eclipse will already be in its total phase and the moon will be a deep-red colour as it climbs into the sky.
The exact time of Moonrise will be at 8.49pm BST in London, 9.46pm in Glasgow, 9.02pm in Cardiff and 9.27pm in Belfast.
The best views - weather permitting - could be across Eastern Europe, Central and East Africa and South East Asia, from where the entire eclipse will be visible.
All you need is a clear view of the night sky. Your eyes are the best instrument to soak up the sight. If you happen to have a pair of binoculars to hand you can use them to range across the craters of the moon but that's just icing on the cake.
While you are out observing the lunar eclipse, stop to take a look at Mars as well. Mars is the closest its been to the Earth for 15 years - and is lined up so it will appear in the same part of the sky as the Moon. Look out for Mars rising about half an hour after the moon. It will be visible to the naked eye and shine more brightly than usual.