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The Keystone

Right Ascension16h42 to 17h16
Declination+30° 54' to +38° 53'
Area (sq deg)37
Brightest StarZeta Herculis
Optimum VisibilityJune
NotesA group of four stars generally seen as representing the body of Hercules, which together form a rough trapezium shape reminiscent of the keystone of an arch. M13, the globular Hercules Cluster, lies along the western edge of the Keystone between the stars Zeta and Eta Herculis.
Map of the Keystone in Hercules Map of the Keystone in Hercules

Imagery provided by Aladin sky atlas


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