The Keystone is an asterism formed by four relatively bright stars in the constellation Hercules: Pi, Eta, Zeta and Epsilon Herculis. The trapezoid-shaped pattern makes it easy for observers to identify the constellation and to find several well-known deep sky objects. On a clear night, the Keystone can be seen between the bright Vega, the brightest star in Lyra, and the stars of Corona Borealis, the Northern Crown. The asterism represents Hercules’ torso.
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