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Hercules
Despite being one of the most ancient of the constellations, Hercules possesses no stars brighter than the third magnitude. However it makes up for this with some very fine objects for amateur telescopes.
The most famous of these is the globular cluster M13, which is one of the showpiece objects of the northern heavens for small telescopes. This spectacular swarm of countless stars, granular in appearance towards the extremely condensed centre, is a wonderful sight with a wide field eyepiece and completely fills the view with higher magnifications. It is located 2.5 degrees south of the top right hand star (Eta) of the so-called “Keystone”. As an additional bonus the 11th magnitude galaxy NGC 6207 may be seen in the same low power field as M13.
In M92 Hercules boasts another very fine globular cluster for small telescopes. Unfortunately M92 tends to get overlooked because of the presence of its larger and brighter neighbour M13.
Hercules is also well endowed with double stars. Particularly notable are Alpha and Delta. Alpha, also known as Ras Algethi, consists of a red 3rd magnitude primary and a blue-green 5th magnitude secondary, giving a wonderful contrast. The primary of Ras Algethi is a massive red supergiant, possibly rivalling even Betelgeuse and Antares in size. Delta, consisting of a blue-white 3rd magnitude primary and yellow 8th magnitude secondary is no less striking, although unlike Alpha the pair are not a true physical double.
M33, the 'Great Globular Cluster'
A further interesting deep sky object in Hercules is NGC 6210, which lies between Delta and Beta This is a typical planetary nebula, better observed with averted vision than directly
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