How to watch the total eclipse of the Moon on July 27th, 2018

How to watch the total eclipse of the Moon on July 27th, 2018

Stages of a total eclipse of the MoonStages of a total eclipse of the Moon
A sequence of images of a previous lunar eclipse, showing the Moon at the start, middle and end of totality. The middle image was exposed longer to bring out the colour within the shadow. Image credit: Paul Sutherland

One of nature’s greatest astronomical spectacles, a total lunar eclipse, occurs on July 27th, 2018, when the Moon glides through the Earth’s shadow in space. 

This will be a total eclipse of the Moon because the Full Moon becomes completely immersed in the shadow, cutting out all direct light from the Sun. (Lunar eclipses can only occur at Full Moon when the Sun, Earth and Moon are in line).

The Moon gives off no light of its own, but usually remains visible during a total eclipse due to some sunlight being refracted through the Earth’s atmosphere and scattered onto the lunar surface.

The scattered sunlight is at the red end of the spectrum, causing the Moon to turn a red or coppery colour. Its brightness during a total eclipse of the Moon will vary, depending on how much dust there is in the Earth’s atmosphere.

It always grows extremely dim compared to the glare of a Full Moon, and you can see the sky become much darker as it does so. This eclipse will be enhanced by the presence of Mars shining brightly close by. The planet is at opposition on the same night. More about what’s in this month’s night sky here.

Unlike a total eclipse of the Sun, which is only visible along a narrow track on the Earth, a total eclipse of the Moon is visible from anywhere where the Moon is above the horizon – that is around half the Earth at a time.

Unfortunately for residents of the USA and Canada, the Moon remains below their horizon throughout the entire eclipse, so they will see none of it other than via webcasts! The total eclipse will be visible from Europe, Africa, Asia, Australia and much of South America.

Our diagram showing key moments as the Moon moves through the shadow of the Earth in space. Note that the Moon moves from right to left through the shadow as it orbits the Earth, but it will appear to move in the opposite direction across the sky as the Earth rotates. (These directions are reversed if you are in the southern hemisphere). Image credit: Skymania

This will be quite a long-lasting eclipse because the Moon passes through the centre of the Earth’s dark umbra, the circular main shadow in space. The time when the whole of the Moon lies in this shadow will last for nearly an hour and three quarters!

What happens when!

The Moon will enter Earth’s lighter outer shadow, known as the penumbra, at 17.15 UT (P1). It will start to enter the darker inner shadow, or umbra, just after 18.24 UT (U1) and will be fully immersed in it by 19.30 UT (U2). At 21,13 UT, the Moon starts to leave the umbral shadow (U3), and it will have exited completely by 22.19 UT (U4). It then passes through the penumbra again before the eclipse ends at 23.29 UT (P4). Use Google to check your local time against UT.

From South America, Europe and western Africa, the Moon will rise during the evening while the eclipse is already in progress. The whole eclipse can be seen from eastern and southern Africa, and Asia. The Moon will set during the eclipse from the Far East and Australia, where it will be the early hours of July 28th. Read our guide to eclipses of the Moon.

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