Europe's total solar eclipse: the ultimate guide to the best places to see it and how to view it safely

A total solar eclipse is a rare and awe-inspiring spectacle that occurs when the moon passes directly between the Earth and the sun, blocking the sun's light and revealing the sun's ethereal outer atmosphere. The last total solar eclipse visible from mainland Europe occurred in 2015 and this year's eclipse will be the first in 20 years.

On Wednesday 12 August, millions of Europeans will be treated to a spectacular sight as a wide band of north and central Spain, plus a sliver of Portugal and parts of Greenland and Iceland experience a total solar eclipse. A partial solar eclipse will be visible in the UK, with viewers in Cornwall experiencing approximately 96% coverage, while those in the west of Scotland will see around 93% coverage and those in London will witness approximately 92% coverage.

A solar eclipse occurs when the moon passes directly between the Earth and the sun, resulting in the moon casting a shadow on the Earth. Viewers see a total solar eclipse when the sun's light is fully blocked by the moon – meaning they are in the umbra of the moon's shadow – and a partial solar eclipse when only part of the light is blocked, meaning they are in the penumbra of the moon's shadow. Dr. Megan Argo, a reader in astrophysics at the University of Lancashire and the vice-president of the Society for Popular Astronomy, notes that 'the moon and sun have to line up precisely for the moon to fully cover the sun and for you to see a total eclipse.'

Whether viewers see a total or partial eclipse – or no eclipse at all – depends upon their location on the Earth's surface. Dr. Argo adds that 'you have to be right in the middle of the shadow to see a total eclipse, and that is quite a narrow track on the Earth's surface.'

This total eclipse will be the first in mainland Europe in two decades, with the last event of this kind visible from the UK occurring in 1999. The next total solar eclipse visible in the UK is not due to occur until 2090. While the country will only experience a partial solar eclipse on Wednesday, experts are enthusiastic, noting that this is 'the best [solar] eclipse that we've had in the UK since 1999.'

For those watching in Spain under the path of the total eclipse, it will peak between 20.26 and 20.33 local time, depending on location, shortly before sunset. In the UK, the Royal Observatory Greenwich calculates that the partial eclipse will begin for viewers in London at 18.17 BST, before reaching its maximum at 19.13 BST and ending at 20.06 BST. Dr. Carys Herbert, an astronomer at Royal Observatory Greenwich, notes that people in Cornwall will experience approximately 96% coverage, while people in the west of Scotland will witness around 93% coverage and people in London will see approximately 92% coverage.

Dr. Herbert stresses that it is crucial not to look at the sun with the naked eye, or to rely on sunglasses, as this can cause permanent eye damage. Instead, experts recommend buying special eclipse glasses. During a 2017 eclipse, Donald Trump was widely mocked for pointing upwards during the solar eclipse without glasses, despite repeated warnings that doing so can lead to permanent eye damage. Dr. Herbert notes that 'if you don't have eclipse glasses, you can use a colander or something to create a pinhole projector.'

This is a way to see the eclipse indirectly – do not look at the sun through the colander but project the light onto card or paper. Assuming that clouds don't block the view, the spectacle will resemble a growing bite being taken out of the sun's disc as the moon moves in front of it, until only a slim crescent is visible. As the moon moves away, the sun will gradually return in its full glory.

There are also scientific advantages to observing a total solar eclipse. Dr. Argo notes that 'there are scientific things that we can do during eclipses,' and these events offer a unique opportunity to study the sun's outer atmosphere – or solar corona. Dr. Argo explains that 'it can tell us a lot about the chemistry of the sun's atmosphere, [and] how the atmosphere varies depending on the sunspot cycle and the solar activity cycle, which goes through an 11-year cycle.'

Additionally, a total solar eclipse allows researchers to study the sun's corona in greater detail than with traditional methods. As the moon passes between the Earth and the sun, it blocks the direct sunlight, revealing the solar corona in all its glory. Dr. Argo notes that 'back in the 1919 solar eclipse, there were expeditions to go and measure the position of the planets and stars close to the sun during the eclipse to basically confirm Einstein's theory of general relativity.'