M37, Open Cluster


Ron Brecher


SBIG STL-11000M camera, Baader RGB filters, 10″ f/6.8 ASA astrograph, Paramount MX. Guided with STL-11000’s internal guider. Focused with FocusMax. Acquisition, guiding and calibration with MaximDL. CosmeticCorrection, Image registration and all processing in PixInsight. Shot from my SkyShed in Guelph, Ontario. Full moon. Average transparency and good seeing throughout.

9x5m R, 11x5m G, and 9x5m B, all unbinned frames (total=2hr25m).

Full processing details are at astrodoc.ca/m37.

M37 is one of my favourite open clusters. It is one of three bright open clusters in Auriga. The others are M36 and M38, both of which I imaged in 2015. All three are great in binoculars or a small telescope, and can be seen with the naked eye from a dark site. Although all three are in Messier’s famous catalogue, they were first recorded by an Italian astronomer, Giovanni Battista Hodierna before 1654. More than 500 stars belong to this triangle-shaped cluster, and it has a mass more than 1,500 times that of the Sun. It’s several hundred million years old, and is about 4,500 light years away. From its apparent size in the sky and this distance estimate, the cluster has been estimated to span 20-25 light years.

This image shows many more stars, better colours and better detail than my 2010 image which was captured with a smaller telescope and a different camera (6″ f/8 refractor and QSI583wsg camera on MI-250 mount).