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The Great Globular Cluster of Hercules
Jon Greif / S&T Online Photo Gallery


Jon Greif

Location of Photo:

La Jolla, CA, USA

Date/Time of photo:

July 1, 2022, between 10 pm and 1 am PDT


Takahashi FSQ-85ED with 1.01 Flattener, ZWO ASI533MC Pro imaging camera, Optolong L-Pro filter, ZWO 30 mm guide scope, ZWO ASI290MM mini guide camera, Rainbow Astro RST-135 mount, ZWO ASIAIR Plus controller and capture software, and Pixinsight 1.8.9 processing software on a Macbook Pro.


An old favorite was in perfect position for imaging from our deck night before last. Over 100,000 stars whirl within the globular cluster M13, aka the Great Hercules Cluster, for the constellation in which it lies. M13 is one of the brightest star clusters visible from the Northern Hemisphere. Located 25,000 light-years from Earth with an apparent magnitude of 5.8, this glittering metropolis of stars can be spotted with a pair of binoculars. The English astronomer Edmond Halley, best known for recognizing the periodicity of the comet that bears his name, discovered M13 in 1714. Charles Messier added M13 to his catalog in 1764. Because they are so densely packed together, the cluster’s individual stars were not resolved until 1779. Near the core of this cluster, the density of the stellar population is about a hundred times greater than the density in the neighborhood of our sun. These stars are so crowded that they can, at times, run into each other and even form a new star. If you look in the upper left corner of this image, you'll see the galaxy NGC 6207. M13 and NGC 6207 may appear close together, but they’re light years apart – literally! While M13 is a “mere” 25 thousand light years away, the light from NGC 6207 comes from a distance of 46 MILLION light years – nearly two thousand times more distant! This image is a stack of 53 one shot color subs of 180 seconds each (2.65 hours) processed in Pixinsight.