Brits will be hoping for a cloudless sky this evening so they can get the best view of the longest total lunar eclipse for a decade.
The event will see the moon turn deep red for 100 minutes during the period of totality.
Views from the UK (and Europe) will be constrained by the fact that the moon will be below the horizon for much of the eclipse, and will rise fully eclipsed, or in some cases even coming out of eclipse.
Here's what to do if you want to see it. Try to find somewhere with a very low and clear south east horizon, as this will be the direction in which the moon will rise, and it will be in eclipse only while it is very low ( a few degrees above the horizon).
Nasa warned Europeans will miss the early stages of the eclipse 'because they occur before moonrise'.
People in the eastern half of Africa, the Middle East, central Asia and western Australia will be able to enjoy the entire event. However, those in the US will miss out as the eclipse will occur during daylight hours.
The moon is normally illuminated by the sun. During a lunar eclipse the earth, sun and moon are in line and the Earth's shadow moves across the surface of the full moon.
Sunlight that has passed through the earth's atmosphere makes the moon appear red, brown or black.
The moon travels to a similar position every month, but the tilt of the lunar orbit means that it normally passes above or below the terrestrial shadow. This means a full moon is seen but no eclipse takes place.
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