Rare blue moon appearing on Sunday May 31 – what it is and best time to see it

The event last happened almost two years ago and will not be seen again until December 31, 2028

Stargazers who look up to the skies this weekend may enjoy a rare treat with a special lunar event which last happened almost two years ago. May 2026 will have two full moons appearing in the same calendar month.

The second full moon, which is known as a blue moon, will rise on Saturday night giving stargazers an extra chance to enjoy one of the year’s most impressive sights. And while it is usually not blue but often just the same colour as a normal moon, there are times when it does change colour.

The event is rare as most months will only have one full moon, with the last blue moon being in August 2024. Astronomy expert Alan Jones from 365 Astronomy explains why this blue moon is unusual, when to see it in the UK, and how to get the best view.

When to see May’s blue moon

Alan explained: “The blue moon reaches peak illumination on Sunday, the 31st, although the best time for stargazers will be on the evening of Saturday, May 30th, when the moon rises shortly after sunset and stays visible throughout the night. It will sit relatively low in the southern sky, so choosing a location with clear views of the eastern and southern horizon, away from tall buildings and trees, will provide the best experience.”

Why this blue moon is special

“A blue moon is the second full moon within a single calendar month, something that happens only every two to three years. Despite the name, the moon will not actually appear blue, ” said the expert.

“This year’s event is also a micromoon, meaning the moon is near the furthest point in its orbit from Earth. It may appear slightly smaller and dimmer than usual, although the difference is subtle.”

Why the moon can appear orange or red

Alan said: “As the moon rises or sets near the horizon, it can take on orange, amber or reddish tones because Earth’s atmosphere scatters shorter blue wavelengths of light. The well-known ‘moon illusion’ can also make the moon appear larger when it is low in the sky, even though its actual size does not change.”

Is the blue moon worth observing?

“Full moons are excellent targets for casual observers, families and beginner astronomers,” said Alan. “A blue moon also carries a sense of rarity reflected in the phrase ‘once in a blue moon’. While not exceptionally rare astronomically, these events still capture people’s imagination and encourage more of us to look up at the night sky.”

Tips for viewing and photographing the moon

“Binoculars are a great way to enhance the view, revealing darker maria and brighter crater regions on the lunar surface,” said the expert. “Smartphones can also capture impressive images when mounted on a tripod and used with manual exposure settings.

“For dramatic moonrise photos, include buildings, trees or landscape features in the foreground to help show the moon’s scale against the horizon. For closer lunar photography, a telescope with an aperture of around 80mm or more will provide crisp detail. Smart telescopes such as the Dwarf 3, Seestar S30 or S50, eVscope 2 and Vespera II are also excellent beginner-friendly options for capturing detailed lunar images.”

When is a blue moon blue

According to the Royal Museums Greenwich there are times that a blue moon actually does appear blue. It said: “Blue moons aren’t blue! Blue moons remain the same colour as any other full moon except in two rare cases:

• During a lunar eclipse, the moon can turn blood red, lit only by the light bent around the Earth by its atmosphere onto the face of the moon. As lunar eclipses occur only during full moons, and blue moons are one type of full moon, it’s very rare that a blue moon will be red!
• In very rare circumstances, the moon can appear blue, but in this case the colour would be caused by viewing the moon through a haze of dust particles in our atmosphere, perhaps from a recent volcanic eruption. From space, however, the moon will look just as grey as it always has!