Astronomy for beginners: How to stargaze at home © Getty Images

How can I see the Great Square of Pegasus?

See this asterism in the autumn sky.

The Great Square of Pegasus is prominent during autumn, and although charts suggest a large, dominant shape, the reality is a little different. The square’s corners are marked by middle-brightness stars easily seen under most sky conditions.

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None of the sides are exactly the same length, on average appearing similar to the distance between your index and little finger when outstretched at
arm’s length.

Technically, the Great Square is an asterism, an unofficial pattern. Its upper-left corner (when viewed from the UK) is marked by Alpheratz, the primary star of Andromeda, the remaining corners belonging to Pegasus. The shape represents the upside-down torso of Pegasus the Flying Horse.

How can I see the Great Square of Pegasus? © Peter Lawrence

Although the Great Square may look empty, faint stars do appear within it and the number seen is a good indication of sky quality. A heavily light-polluted sky will show none. Up to five is average, with up to 13 really good. Under exceptional circumstances, 35 stars can be counted within the square with the naked eye.

If your skies are dark, once you’ve identified the Great Square, look a square-side length below it to locate a faint circle of stars. This is the Circlet, another asterism representing one of the fish in Pisces the Fishes.

When the Great Square lies high in the south, follow its right side down towards the horizon to locate Fomalhaut, the brightest star in Piscis Austrinus, the Southern Fish. The left side of the square points down to Deneb Kaitos, the brightest star in Cetus the Whale.

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