Messier 72

M72 by Ron Brecher.

M72 by Ron Brecher.

Ron Brecher

Guelph, Ontario, Canada

SBIG STL-11000M camera, Baader Ha, R, G and B filters, 10″ f/6.8 ASA astrograph, Paramount MX. Guided with QHY5 guide camera and 80 mm f/6 Stellar-Vue refractor. Acquisition, guiding and mount control with TheSkyX. Focusing with FocusMax. Automation with CCDCommander. All preprocessing and post-processing in PixInsight. Shot from my SkyShed in Guelph, Ontario. No moonlight. Good to excellent transparency and seeing for acquisition of Luminance. Poor to average transparency and seeing for acquisition of R, G and B.

6x10m R, G, B and L unbinned frames (total=4hr).

Complete processing details at

M72 is a globular cluster in Aquarius. It’s not the splashiest object of this type, often being overlooked for nearby M2 and M22. In fact, it’s interesting to compare M72 and M22. They are quite different when you look at them side by side at the same image scale. And the numbers bear out the visual impression. Compared to M22, M72 is about

– 40 times fainter (at magnitude 9.5),
– 5 times further away (at 55,000 light years),
– about 1/5 the visual size (at a little more than 1/3 the moon’s width)
– about half the size (168,000 stars vs. almost 300,000)
– 2.5 million years younger (at 9.5 billion years old)