α Ophiuchi and α Herculis are only about 5° apart.
The cluster 13 M., the Halley Nebula, can be easily seen in an opera-glass. In a recent photograph of this cluster 50,000 stars are shown in an area of sky which would be entirely covered by the full moon.
Hercules occupies the part of the heavens toward which the sun is bearing the earth and planets at the rate of twelve miles a second or 373 million miles a year.
On a clear night the asterism Cerberus, the three-headed dog, which Hercules holds in his hand, can be seen.
This constellation is said to have been an object of worship in Phœnicia. There is a good deal of mystery about its origin. The ancient Greeks called it "The Phantom" and "The Man upon his Knees."
The stars ε, ζ, η, and π form a keystone shaped figure that serves to identify the constellation.
