M33 is one of the closest spiral galaxies lying at a distance of 2,723,000. It therefore appears large and also presents us with a nearly face-on view. As such, it reads like an open book on all the processes we can see going on in a spiral galaxy. Dark dust clouds condense into hot blue supergiant stars. They emit intense ultraviolet radiation that strike the remaining hydrogen gas in the cloud and cause it to glow red as an emission nebula at the hydrogen-alpha frequency of 656.28 nm. They also emit fierce stellar winds that drive the gas away and the stars within the nebula become unbound and spread out as an OB association of blue supergiants. But those blue supergiants live fast and die young as supernovae within a few million years. The shockwaves from the supernovae compresses gas in neighboring dark clouds, causing them to collapse and the process repeats. As the galaxy rotates over millions of years, these processes trace out curving spiral arms of blue supergiants ornamented with red emission nebulae. Compare this image with my previous image of M33 taken with the Celestron Compustar C14, shown under Galaxies. The difference in sharpness, clarity, and detail is jaw-dropping.

Telescope/Mount: PlaneWave CDK17 on L500 mount.

Exposures: Ha:L:R:G:B = 480:460:110:110:110 minutes = 21 hours, 10 minutes total exposure at f/6.8/