What is a lunar eclipse?

An eclipse of the Moon occurs when the Earth lies directly between the Sun and the Moon and the Moon lies in the shadow of the Earth. For a total lunar eclipse to happen, all three bodies lie in a straight line. This means that the moon passes through the darkest part of the Earth’s shadow - the umbra.

Watch the animation below to find out more about what happens during a lunar eclipse.

Total lunar eclipse

During a total lunar eclipse, the Moon usually turns a deep, dark red because it is illuminated by light that has passed through the Earth's atmosphere and has been bent back towards the Moon by refraction.

Glass lantern slide of a lunar eclipse taken 16 November 1910 - unknown artist 1.jpg

Partial lunar eclipse

During the partial phase of the eclipse, part of the Moon travels through the Earth's full 'umbral' shadow. However, on this occasion only a very small section of the Moon will be covered by the umbra at maximum eclipse, though the whole northern half of the Moon will be darkened by the penumbral shadow.

Jon Culshaw is a judge for the Insight Investment Astronomy Photographer of the Year competition. Find out more

Penumbral lunar eclipse

A penumbral lunar eclipse occurs when the Moon travels only through the outer, fainter part of the Earth's shadow, or 'penumbra'. This happens when the Earth moves between the Sun and Moon but the three do not form a perfectly straight line.

The penumbra causes only a slight darkening of the Moon's surface, with the Moon still exposed to some direct sunlight, so this type of eclipse is easy to miss.

When is the next lunar eclipse in the UK?

A partial lunar eclipse, barely visible in the UK, will next take place on 19 November 2021. However, there will be a longer wait for the next total lunar eclipse.

19 November 2021 Partial lunar eclipse
16 May 2022 Total lunar eclipse 

On 16 May 2022 a total lunar eclipse will be visible over South America, most of North America and parts of Europe and Africa.

People in the UK will not be able to see every part of the eclipse but will still be able to see the lunar eclipse at totality when the entire Moon turns red.

The Moon will start to enter the Earth’s shadow just after 2.30am BST and the full eclipse will occur just before 4.30am.

The entire eclipse lasts for more than five hours, ending at 7.50am. However, observers in the UK will only be able to see the eclipse from 2.32am – 5.10am as the Moon will have set below the horizon by the end of this period.

The optimal viewing time to see the eclipse is between 4.29am – 5.06am. This is the period of totality in London, where the Moon lies entirely in the Earth’s umbra (full shadow) appearing red and the whole of the Moon will still be visible.

When is the next full Moon?

How to see a lunar eclipse

See astronomer Tom Kerss's top tips for observing and photographing a lunar eclipse in the video below.

What time is the 2022 total lunar eclipse?

The table below lists the timings for the whole 2022 eclipse as seen from London and they might differ by a few minutes for other parts of the UK.

Local time (BST) in London




Penumbral eclipse begins

The Moon will start to enter the Earth’s penumbra (area of partial shadow) and start to darken.

Low in the south west


Partial eclipse begins

The Moon will start to enter the Earth’s umbra (area of full shadow) and leave its penumbra and will darken considerably, almost as if it is changing its phase from full moon to waning crescent in just over an hour.

Very low in the south west


Full eclipse begins

The Moon has completely entered the Earth’s umbra and starts to turn red.

Very low in the south west



Maximum eclipse

This is when the Moon is closest to the centre of the Earth’s umbra. The maximum eclipse in London is at 5.06am as this is the point at which the entire Moon is still above the horizon at the greatest magnitude Moonset is at 5.10am. The actual maximum eclipse is at 5.11am however the Moon will be below the horizon at this time and as it sets 

Below horizon


Full eclipse ends

The Moon will start to leave the Earth’s umbra and enter its penumbra losing its red colour.

Below horizon


Partial eclipse ends

The Moon has left the Earth’s umbra and has completely lost its red colour. One side starts to get lighter whilst the other is still very dark as it enters the Earth’s penumbra, almost as if it is changing from a waxing crescent to a full moon in around an hour.

Below horizon


Penumbral eclipse ends

The Moon will look slightly darker than usual and has now left the Earth’s penumbra.

Below horizon

When was the last lunar eclipse in the UK?

16 July 2019 - partial lunar eclipse 

A partial lunar eclipse took place in the UK on 16 July 2019, coinciding with the 50th anniversary of the Apollo 11 launch. Some of the eclipse was visible over parts of Europe, Asia, Australia, Africa, select parts of North America, South America and Antarctica.

20-21 January 2019 - total lunar eclipse

A total lunar eclipse took place in the UK in the early hours of 21 January 2019. The eclipse happened during the first full moon of the year, earning it the nickname 'Super Wolf Blood Moon'.

Royal Observatory Greenwich broadcast a live stream of the total eclipse via Facebook. Watch the video back below.

How often do lunar eclipses happen?

A lunar eclipse happens between two to five times a year, with a total lunar eclipse occurring at least two every three years. 

Why doesn't a lunar eclipse happen every month?

A lunar eclipse occurs during the full moon phase but an eclipse does not happen every month, even though the lunar cycle is 29.5 days. This is because the moon’s orbit is inclined by 5˚ relative to the Earth’s orbit. This means that as it travels around the Earth it also moves up and down in its orbit. 

How long does a lunar eclipse last?

Since the Earth is around four times wider than the Moon, its shadow can darken the moon for up to five hours depending on conditions. Lunar eclipses can be seen between two and five times every year – from somewhere on the Earth’s surface. Total lunar eclipses are much rarer from one particular location.

What is a supermoon?

When the moon is close to perigee, the closest point to Earth in its orbit, it makes the moon appear slightly larger than usual. This phenomenon has been dubbed a “supermoon”. Much like “blood moon” it is not an official astronomical term. A “supermoon” will appear up to 7% larger than a regular full moon.

Find out more about supermoons

Why are blood moons red?

People sometimes refer to a lunar eclipse as a ‘blood moon’ because of the way the Moon can turn a deep coppery red colour during its eclipse.

However, the colour of the Moon during totality will depend on the global state of dust in the Earth’s atmosphere – sometimes red or possible virtually invisible. Dust in the atmosphere blocks out the higher frequency blue light waves, but the longer wavelength of red light comes through.

How to see the Super Flower Blood Moon

A Tainted Eclipse © Phil Hart, Astronomy Photographer of the Year Our Moon Commended 2015

This article has been written by an astronomer at the Royal Observatory Greenwich