M5: A globular cluster is a group of ancient stars (M5 is thought to be more than 11 billion years old; by comparison, our sun is about 4.6 billion years old; our galaxy is about 13.5 billion years old, and the universe is thought to be 13.8 billion years old), gravitationally bound to each other, orbiting the core of its associated galaxy.

The glow in the upper right of the image is a very bright star (much closer to us than the cluster), just off the frame.

M5 is about 25,000 light years from Earth, and is about one-quarter of the angular size of the full moon when viewed from very dark skies; it is roughly 80 light years across. It shines at magnitude 5.6 (barely visible, in very dark skies, to the naked eye, but easily seen with binoculars). It has a mass equal to about 850,000 times that of our sun, and contains more than 100,000 stars (for comparison, there are estimated to be no more than 2,000 stars within 50 light years of earth, which is a slightly larger bubble).

Technical Information:

LRGB: 295:120:120:176; luminance layer consists of a blend of 52 five-minute images and 35 one-minute images; RG channels consist of the combination five-minute images, while B was a group of 6.5-minute images.

Equipment: RC Optical Systems 14.5 inch Ritchey-Chretien carbon fiber truss telescope, with ion-milled optics and RCOS field flattener, at about f/9, and an SBIG STX-16803 with internal filter wheel (SBIG filter set), guided by an SBIG AO-X, all riding on a Bisque Paramount ME German Equatorial Mount.

Image Acquisition/Camera Control: Maxim DL, controlled with ACP Expert/Scheduler, working in concert with TheSky X.

Processing: All images calibrated (darks, bias and sky flats), aligned, and combined in Pixinsight. Color combine in Pixinsight. Some finish work (background neutralization, color calibration, gradient removal, Multiscale Linear Transform, lessening the dynamic range) done in Pixinsight; some finish work (Neat Image noise reduction, LRGB combination, contrast and saturation adjustment) was done in Photoshop CC.

Location: Data acquired remotely from Sierra Remote Observatories, Auberry, California, USA.

Date: Images taken during six nights in late June of 2022. Image posted August 1, 2022.

Date: Image scale of full-resolution image: 0.56 arcseconds per pixel.

Seeing: Generally good, with calibrated luminance images varying from 1.9 to 2.2 arcsecond FWHM

CCD Chip temperature: -25C

Copyright 2022 Mark de Regt

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