Partial Solar Eclipse

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Tomorrow, Saturday 29 March 2025, the Moon will pass between the Earth and the Sun, causing a partial eclipse of the Sun. This is not a total eclipse (when the three bodies line up perfectly) but nevertheless, between 30 and 40% of the Sun’s surface will be in shadow at the peak. If weather permits, the eclipse will be visible in the UK from 10:07 am (GMT) until 12:00 pm. Maximum coverage will occur at 11:03 am.

Partial solar eclipse March 2015 Emma Lord Sagacious Cat
Partial solar eclipse 20 March 2015

Types of Eclipse

There are four different types of solar eclipse. The total eclipse occurs when the Moon lines up exactly between the Sun and Earth. The maths is interesting here – the Sun is around 400 times further from Earth than the Moon is, and it’s also around 400 times larger than the Moon. Which means that viewed together, both look to be a similar size. Hence, if the orbit aligns, the Moon can block the Sun completely. The next total solar eclipse visible from the UK is on 23 September 2090.

An annular eclipse occurs when the Moon is at a slightly different stage of its orbit and further from the Earth. Although the three bodies are aligned, the Moon does not cover enough of the Sun’s surface to block it out completely and a halo of light remains visible.

A partial eclipse happens when the Earth, Moon, and Sun are aligned, but not quite enough in line for the Moon to cover the Sun completely.

solar eclipse March 2015 Emma Lord Sagacious Cat
Figures in a landscape – partial eclipse on 20 March 2015, when around 80% of the Sun was obscured. This was the view on The Ridgeway at peak coverage (around 9.30am in the UK).

Finally, the rarest type is a hybrid eclipse. Around 3% of eclipses fall into the hybrid category in which the eclipse changes type during the event. This is due to the elliptical orbit of the Moon around Earth. The distance between the two bodies is changing constantly. If the Moon is at the critical point in orbit, what starts as an annular eclipse might become a total eclipse. Or vice versa. In some cases the pattern will go from annular to total and return to annular.

Viewing

It is important not to look directly at the Sun during an eclipse. The exception to this advice is the brief time of totality during a total eclipse. At this point, the sky resembles twilight and the Sun may be viewed safely. The duration of totality varies from a few seconds to minutes, depending on location.

The safest option is to source solar eclipse glasses from a trusted organisation. This year, I bought some from Go Stargazing, an organisation which aims to encourage interest in astronomy a wide audience.

solar eclipse glasses March 2025 Emma Lord Sagacious Cat

Money raised through the sale of glasses goes towards Astronomers Without Borders. This community works to bring people around the world together to appreciate astronomy and enjoy learning about the universe.

If you are unable to view the eclipse from home, the Royal Observatory Greenwich is live streaming the event on YouTube from 10:00 am. More details are available on their website.

Here’s hoping for good weather, and a great celestial show tomorrow. If you miss it, there is a partial solar eclipse here in the UK every year until 2030. The next is a large one on 12 August 2026. At its peak (7:13 pm) around 90% of the Sun will be blocked. This is an easy date for me to remember as it’s a special birthday for a close relative. I won’t embarrass him by mentioning his name, although I call him Dad.