Introducing the Hercules Globular Cluster aka the Great Globular Cluster in Hercules (Messier 13 or NGC 6205). I haven’t stopped marveling at the thought of so many stars packed into so relatively dense a structure as this. Or even that something like this is possible.

This bright gob o’ light is a globular cluster comprised of several hundred thousand stars in the constellation of Hercules. A globular cluster is a tightly packed group of old stars which are packed closely in a symmetrical form. Globular clusters formed from giant molecular clouds, or huge masses of gas which form from stars as they collapse. Globular clusters are older structures relative to the universe as less free gas is available today for formation of globular clusters than was the case when the universe was denser.

In 1716, English astronomer Edmond Halley noted of the Hercules Globular Cluster, “This is but a little Patch, but it shews itself to the naked Eye, when the Sky is serene and the Moon absent.” To the human eye, under sufficiently dark skies with binoculars, the Hercules Globular Cluster looks like a dim and somewhat hazy star. The Hercules cluster is one of the brightest globular clusters visible in the northern hemisphere and is about 145 light years in diameter (our Milky Way is over 100,000 light years) by way of comparison and is 22,180 light years from earth.

Technical Details:

This photograph was created using a large quantity of individual exposures captured with a telescope, astronomy camera, and an equatorial mount. Processing was done in PixInsight and Adobe Photoshop.

I didn’t capture these exposures with any particular plan in mind. I just had so much data on this target that I went back and used a lot of my best data to create this final image. It would have been sensible to produce this image with one telescope (e.g. the 120 ED) and camera (e.g. 2600MC or 2600MM combining sessions of luminance and RGB). A bright globular cluster also does not require so much integration time.

CEM-70g, Esprit 120 ED + APEX-L, 183MC, N/A
- 2021-01-11, 2021-01-14, 2021-01-15
- 42x10s and 38x30s, Bortle 7-8
CEM-70g, Esprit 120 ED, 2600MM, Astronomik L2
- 2021-02-25, 2021-03-01, 2021-03-05
- 28x10s and 78x30s, Bortle 7-8
CEM-40EC, Esprit 80 ED, 2600MC, N/A
- 2021-03-12, 56x120s, Bortle 7-8
CEM-40EC, Esprit 80 ED, 183MC, N/A
- 2021-04-01, 125x30s, Bortle 7-8
CEM-40EC, RASA-8, 2600MM, Astronomik L1
- 2021-04-19, 86x30s, Bortle 4
CEM-40EC, Esprit 80ED, 2600MM, RTU
- 2021-04-28, 87x60s, Bortle 7-8
CEM-70g, Esprit 120ED, 2600MM, Astronomik L2
- 2021-05-14, 30x60s, Bortle 4

Total Integration Time
6 hours, 44 minutes, 10 seconds

Separate sessions calibrated with darks, flats (typically sky flats), and dark flats. Sessions were stacked, background light gradients extracted, calibrated, and then combined into a few monochrome masters (combined selectively for the best result) and a series of color images used for color.

Photographs captured in Salt Lake City, Utah, and Antelope Island State Park, Utah