Stargazing Challenges - October 2026

Challenge 1 - The Keystone Asterism

Whilst facing in a westerly direction, try looking for a familiar star pattern in the constellation of Hercules known as the Keystone asterism. It will be visible throughout October, but towards the end of the month it’ll appear closer to the horizon when viewing at the same time.

Hercules is the Roman name for the Greek demigod Heracles, famed for his mighty strength and courage. The constellation is best seen in the night sky between the spring and autumn in the UK and is the fifth largest of the 88 constellations identified by the International Astronomical Union (IAU). Hercules can quickly be recognised by spotting four stars in a lopsided square shape that make up the torso of the hero, known as the Keystone asterism. It gets its name from an architectural term: a keystone is the central stone at the top of an archway that holds the whole structure together.

Along the perimeter of the Keystone asterism is a deep sky object known as the Hercules Globular Cluster, which is a densely packed group of several hundred thousand stars located roughly 25,000 light years away. To the naked eye on a dark night, it will appear as a fuzzy blob and is one of the brightest globular clusters visible form the Northern Hemisphere. With a pair of binoculars or a small telescope, you’ll be able to resolve a hazy round patch and with a larger aperture telescope, you could even resolve or separate individual stars.

The M13 Globular Star cluster contains the famous ‘blue straggler’ stars which were the target of the 1974 radio transmission known as the Arecibo message. This interstellar message included some basic information about humanity and Earth, and was intended to demonstrate how we could initiate contact with potential intelligent extra-terrestrial life. The message has a long journey time though, about 25,000 years!

Challenge 3 - Full Moon

Look to the eastern horizon as the Sun sets at around 18:00 to see October's full moon. During a full moon, our natural satellite is positioned on the opposite side of the Earth to the Sun so its face is fully illuminated by sunlight. As the night continues, the Moon will make its way across the sky towards the western horizon until the Sun rises again, so you'll be able to observe it all night long.

Each month, the full moon is given a traditional name which reflects agricultural and seasonal changes. These are taken from native, colonial American and European cultures. This month’s full moon is called the Hunter's Moon, and is named to mark the best time of the year to hunt, as animals would be plump from abundant food throughout the summer. You can find our full moon calendar and more information on native full moon names in our Full Moons and Full Facts blog.

Full moon FAQ - Water on the Moon

Whilst several surface features on the Moon follow a marine-based naming convention, such as the Sea of Tranquillity where Apollo 11 touched down in 1969, we have long considered the Moon to be nothing more that a dry barren rock. Recent evidence, however, has suggested that this may not be the case.

In 2008, India's Chandrayaan-1 mission detected hydroxyl molecules spread across the lunar surface, and NASA missions such as Lunar Prospector, LCROSS, and the Lunar Reconnaissance Orbiter, have detected water ice in the permanently shadowed regions of the lunar poles. This is an incredibly important discovery, as if we want to send astronauts to the lunar surface for extended periods of time, such as with the Artemis Program, then having water already on the Moon that we can extract saves a lot of launch mass. Not only that, but water, or H₂O, can be split via electrolysis to make rocket fuel.