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The century's longest lunar eclipse

The Sun, Earth and Moon are set to fall perfectly in line.
The Sun, Earth and Moon are set to fall perfectly in line. / SUR
  • The blood moon eclipse will be visible over much of the planet

We are in for a real treat this evening (Friday 27 July) - a total eclipse of the Moon. A lunar eclipse occurs when the Sun, Earth and Moon line up perfectly and the Moon passes through the shadow cast by the Earth.

An eclipse of the Sun occurs when the line-up is the other way round and the Moon's shadow falls upon the Earth.

Whereas an eclipse of the Sun can only be seen from a small area along a very narrow band where the shadow touches the Earth, an eclipse of the Moon can be seen from any part of the planet where the Moon can be seen. Tonight's eclipse will be visible to more than half of the Earth's population.

From Spain the eclipse will already be under way as the Moon rises in the southeast at 8.30pm. It may be difficult to see the Moon at first as it rises because it will be in shadow.

It won't go completely black but instead will turn a very deep red in colour. This is because light from the Sun will be scattered through our atmosphere giving it a red hue. A lunar eclipse is sometimes known as a "blood moon" because of the colour.

Try to get as clear a view of the southeastern horizon as you can manage; on the beach would be best but anywhere away from trees or houses.

As the Moon continues to rise it will move deeper into the Earth's shadow. Unlike an eclipse of the Sun, which lasts for only a few short minutes, a lunar eclipse can last for several hours. This eclipse will be the longest this century as the Moon will pass through the widest part of the Earth's shadow.

At 9.30pm the Moon will be at the centre point of the eclipse. At about 10.15pm it will slowly emerge from the shadow and begin to brighten again along the left-hand side. At around 11pm you should be able to see the curve of the Earth's shadow along the centre of the Moon running north to south. The eclipse will end at 11.15pm.

While you are admiring the eclipse, make a note of the bright red 'star' just below and to the right of the Moon.

This is the planet Mars and this weekend it will be at the closest point to the Earth in over 60,000 years. It will be shining even more brightly than the planet Jupiter and should make a tremendous view with the eclipsed Moon so close by.

Members of the Fuengirola Astronomy Society will be holding viewing sessions at the top of Benalmádena to watch the eclipse and see Mars through giant telescopes. Take the cable car up from Tivoli World.