M2: A globular cluster is a group of ancient stars (M2 is thought to be about 13 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.

M2 is in an unusually unpopulated part of the sky; normally, a field I shoot is full of background galaxies, and there are relatively few in this field.

M2 is about 55,000 light years from Earth, and is about one-fifth of the angular size of the full moon when viewed from very dark skies; it is roughly 175 light years across. It shines at magnitude 6.5 (barely visible with the naked eye in the darkest skies, but easily seen with binoculars). It contains about 150,000 stars (for comparison, there are estimated to be no more than 2,000 stars within 50 light years of earth). M2 has a very faint tidal tail (not visible in my image), thought to be the result of an interaction with the Large Magellanic Cloud.

Technical Information:

LRGB: 255:60:55:72; luminance layer consists of 51 five-minute images; R and G 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 (autocolor, gradient removal, BlurXterminator; NoiseXterminator) done in Pixinsight; some finish work (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 on a number of nights in mid-November of 2022. Image posted March 10, 2023.

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

Seeing: Generally good, with calibrated luminance images varying from 1.8 to 2.2 arcsecond FWHM

CCD Chip temperature: -25C

Copyright 2022, 2023 Mark de Regt

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