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π Herculis

Pi Herculis is a reddish star with a magnitude of 3.2. The star forms the northeastern corner of the 'keystone' of the constellation, the central quadrangle.

The binocular view of pi reveals an interesting asterism which is a handy point of repair should one become lost amongst the other stars in Hercules: binoculars.

The star just over one degree to the east of pi, rho Herculis, is a telescopic binary (Struve 2161) with lovely colour contrast of yellow and blue: 4.5, 5.4; 319º, 4.1".

From pi you can find the other corners of the 'keystone', the lopsided square that forms the centre of the constellation. To the southwest a little over one binocular field are zeta and epsilon, while to the northwest of pi about one and a half binocular fields is eta and the fine globular cluster M13.

Click on zeta on the map for the Great Globular Cluster (M13).

However outstanding you will find M13, you shouldn't overlook the other Messier in Hercules, M92. Found one binocular field north of pi, M92 is a rich globular cluster not impressive in binoculars, but with large telescopes quite extraordinary—not to be missed.

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