M13 - The Hercules Cluster

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M13, the Great Hercules Cluster, in LRGB with synthetic luminance.

Location: Comanche Springs, 3RF dark sky site near Crowell, Texas

Date: May 19, 2005

Seeing: 5/10

Transparency: 8/10 (mag. 3.5 skies, 11 day moon)

Temperature: 62 degrees F (-15 degrees C on camera)

Scope/Mount: 12.5" RCOS RC @ f/9 and Paramount ME

Camera: SBIG STL-11000M astro CCD camera

Exposure Info: LRGB image; 45:30:45 RGB with synthetic luminance (5 minute subexposures all unbinned)

Processing Information: Calibration (darks/flats), registration, gradient removal, DDP, and RGB channel combine in MaxIm DL 4 (Sigma median). LRGB combine, cropping, color balance, levels/curves, sharpening, and noise removal (despeckle and gaussian blur) in Photoshop CS.

Exposure Notes: I normally don't image with the moon so bright, but bad weather made me desperate! Still, such an object doesn't require very dark skies, and the magic of image processing really helps to even the background caused by the bright moon. It should be noted that the RC still isn't optimally collimated and aligned yet.

About this Object

Known by most as the most spectacular globular cluster in the northern sky, the Great Hercules Cluster can often be seen with the naked eye in dark skies. As globular clusters go, this cluster, also known as Messier 13, is quite large in size from our perspective, approximately 20 arc minutes wide. The star at the upper-left of this image is a 6.86 magnitude K2 spectral star.

M13 is very easy to find in the night sky, making it one of the first deep sky objects found by beginning hobbyists. Just look to the western side of the Hercules "keystone" and search along that line about 1/3 the way from the northern-most star on that side. Any scope can detect the object, but the individual stars in the cluster need 6 to 8 inches of aperture to really appreciate.

🤖 AI-drafted · unverified

What it is: M13, the Great Globular Cluster in Hercules, is one of the brightest globular clusters visible from the Northern Hemisphere, containing several hundred thousand stars packed into a compact sphere.
Constellation: Hercules
Distance: ~22,200 light-years
Apparent magnitude: 5.8
Angular size: ~20 arcminutes
Coordinates: RA 16h 41m 41s, Dec +36° 27′ 37″

This summary was generated by an AI assistant from general astronomical references, not from Jay's own notes on this specific image. Treat every detail above as a starting point for research, not settled fact.