Wednesday , June 16 2021

How to see the total lunar eclipse in the UK. Top tip: look up

After a week of political turmoil, here's one good reason to be glad you're living in the UK: in the very early hours of Monday morning, our divided kingdom will be one of the best places in the world to watch the next lunar eclipse .

Early risers and late-night owls will start seeing the Earth's shadow cover the Moon from 2:35 GMT until the eclipse ends at 7:49 GMT.

While lunar eclipses are not a rare occurrence – they happen two or three times a year – the UK will be treated to an impressive show. As the entire eclipse happens before the Sun comes up, skywatchers will be able to enjoy it from start to finish; something that happens again until 2029. The previous lunar eclipse, which happened last July, was already about half way through when night started falling in the UK, which means that the Moon had already reached its peak eclipse when it rose. This time, assuming the weather is clear, you should be able to watch all the different stages of the process.

What is so special about any eclipse anyway?

An eclipse happens when the Sun, Earth and Moon align. In reality, that happens every month or so; every time we get a full moon, to be precise. Lunar eclipses, however, happen when this alignment coincides with the Moon going through the Earth's shadow.

“A way to picture it is to think of the Earth's shadow as a projected into space,” says Chris North, a science lecturer at Cardiff University. “A full moon will be roughly opposite the Sun in the sky, which is why we can see it fully lit; but it will be slightly above or below the cone. ”

In contrast, during a lunar eclipse, the Moon finds itself going through the cone of the Earth's shadow. And because the Moon does not emit light, but reflects the Sun's rays, it becomes darker – at least when seen from our planet.

Of course, the Moon orbits around the Earth, which means that an eclipse is a gradual process: the Moon becomes darker than the creeps deeper into the Earth's shadow. In its cone of shadow, the peripheries, where the shadow is, are called the penumbra; and the center of the cone, where the shadow is the deepest, is the umre.

So what can you expect?

The eclipse starts when the Moon enters the penumbra. At that stage, which will happen on Monday, at 02.35 GMT, the Earth is still blocking the whole of the Sun, so the Moon still gets lots of sunshine – observers will only notice that it is darkens slightly.

The real show will kick off at 03:33 GMT, when the Moon enters the track: that's when and where the Earth's core shadow starts taking over. You should see a black wedge munching the Moon away and growing bigger.

While the Moon is still partly in the penumbra and partly in the cubes, the eclipse is partial – and indeed the Moon is still partially colored. The total eclipse starts when it has completely entered the umbra. If it's peak eclipse that you are after, set your alarm at 04:41 GMT.

Last July's lunar eclipse was the longest total eclipse of the century, lasting one hour and 43 minutes. This year, the Moon will start leaving the umbra just over an hour after it has fully entered it – at 05:43 GMT – and will have exited the penumbra at 07:49 GMT.

What with the red moon hype?

In theory, once the Moon is completely within the Earth's shadow, it should be completely dark, and therefore invisible, right? Well, not exactly. Once the Moon is in the umbra, the Earth's atmosphere still acts as a lens that refracts the Sun's light and "fills in" the Moon. Molecules in the Earth's atmosphere scatter the Sun's blue light, while bending its red lights and therefore letting them travel all the way to the Moon. This is the same phenomenon, in fact, that explains why we can save sunsets.

In the case of a lunar eclipse, it means that while the Moon is in the Earth's core shadow – this time, between 04:41 and 05:43 GMT – it will appear red. But what kind of red? Well, we'll know until the Moon's color will depend on the Earth's atmospheric conditions. "Typically, volcanic eruptions can make the moon look more because of the dust particles they bring into the atmosphere," says North. “We had the Anak Krakatau option a few months ago, so maybe that will have some sort of effect.”

How can you get a Instagram worthy shot?

A red moon looks good on a social media feed, but since its very nature is lack of sunlight, it may prove to be a photographic challenge. Use multiple exposures to compensate for the lack of light, and make sure you have a tripod to stabilize your pictures, especially when using a telephoto lens with a long focal length.

The partial eclipse may prove to be an interesting subject to photograph, too. To the naked eye, it will look like the Moon is divided between a pit-black wedge and a bright white side. North explains that in reality, the darker side will already be edited, but the contrast between the two sides is too sharp to let us see it. “You can pull it out with photos,” he says, “although the imbalance in brightness is so great that you would have to think over the color of the moon to see any red.” And if you have only come with your eyes , you will have to wait until the Moon has fully entered the umbra to see the turn saved.

What if you miss it?

Lunar eclipses are fairly regular, and your next opportunity to watch one will be on July 16 – although it will be a partial one, which is arguably of less interest. In any case, there is no reason to get FOMO: if there is one thing that lunar eclipses do well, it's predictability. So make sure you keep an eye on NASA's table of future eclipses for the rest of the century.

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