Emission Nebula Sh2-72


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. Nearly full Moon for Ha and first quarter moon for RGB. Good to excellent transparency and average to very good seeing throughout acquisition.

4x15m R, 4x15mG, 4x15mB and 36x20m Ha unbinned frames (total=15hr).

Complete processing details at astrodoc.ca/sh2-72

Sh2-72 is an emission nebula in Aquila, the Eagle, and lies about 5,870 light years away in a rich star field. This object also goes by the catalogue number RCW179. There appears to be some active star formation going on in this gas cloud based on infrared observations. Like other emission nebulae, the red colour of Sh2-72 comes from hydrogen atoms releasing energy as red light. The varied star colours indicate their temperatures: hot stars are blue and white; the coolest stars are reddish.

The colour image blends the red, green and blue colour channels with data collected through a deep red H-alpha filter. The black and white image shows the H-alpha data alone.

I have been shooting dim members of the Sharpless catalogue over the last few months. They are challenging to image (actually, to process), since detail is subtle and the targets I’ve chosen are very faint. But that is half the fun!