The Globular Clusters of Hercules

Globular star clusters are tight collections of tens of thousands of stars in a relatively compact region of space. They surround our Milky Way Galaxy in sort of the same way as a swarm of mosquitos might surround your head in a swamp. They are much prettier to look at than mosquitos and certainly much larger, however. There are about 150 known to be associated with our Milky Way Galaxy. In the sky most of them are found in the constellations Scorpius, Sagittarius, and Ophiuchus in the summertime Southern sky. Three nice ones can be found in the constellation Hercules which is now high in the Eastern sky at our latitude. We recently photographed all three one clear night with our 16” Cassegrain telescope.

M13

This star cluster is one of the brightest that can be seen from the northern hemisphere. Even with the naked eye through a good eyepiece on our 16” Cassegrain, several dozen individual stars can be resolved. Of course the camera makes many hundreds visible.

M92

This star cluster is only slightly dimmer than M13 and is always rewarding to look at. It is interesting to remember that 200 years ago astronomers were only just starting to realize that these globular clusters were made up of individual stars and were not just fuzzy balls of dust.

NGC 6229

This cluster is definitely the dimmest of the three at only an apparent magnitude of 9.8. All three images are at the same scale so the size comparisons are true, but this image was taken with a longer exposure to make it visible.