Whirlpool Galaxy


Ron Brecher

Ontario, Canada

SBIG STL-11000M camera, Baader HaLRGB filters, 10″ f/6.8 ASA astrograph, Paramount MX. Guided with QHY5 and 80 mm f/6 Stellar-Vue refractor. Focusing with FocusMax. Acquisition with TheSkyX. Automation with CCDCommander. Calibration, registration, integration and all processing in PixInsight. Shot from my SkyShed in Guelph, Ontario. Moderate moonlight for RGB, no moon for L; gibbous to full moon for Ha.

22x10m R, 19x10m G, 17x10m B, 21x15m L, 14x5mL and 18x20m Ha unbinned frames (total=22hr).

Complete processing details at astrodoc.ca/m51/

have taken images of the Whirlpool Galaxy before, several times in fact, with different telescopes and cameras over the years. This shot is my best result yet, and contains data acquired during March and April 2016.

M51 is the galaxy in which spiral structure was first seen, by Lord Rosse in 1845 using a 72-inch telescope known as the “Leviathan of Parsonstown.†The galaxy was discovered in 1773 by Charles Messier. It’s fairly bright and I’ve seen it in binoculars in a reasonably dark sky.

Left of the Whirlpool Galaxy is NGC5195. The two are interacting, and you can see that the smaller galaxy has distorted M51’s arms. M51 has also smeared out its companion, towards upper left and lower right. The pair lie about 30 million light years away, beneath the end star of the handle of the Big Dipper. The Whirlpool Galaxy is about 60,000 light years across and has a mass of around 160 billion times that of our Sun. The pink features in M51 are emission nebulae, similar to the Rosette Nebula in our galaxy. The knots in the blue arms are star clusters, similar to M35 and NGC2158.

M51 and NGC5195 are the largest members of the M51 Group of galaxies. You can see several other members throughout this field. This group and two others (the M101 group and the NGC5866 group) may be part of a single, large, loose group of galaxies, since all lie at similar distances.