The Ring Nebula Revisited
Messier Catalogue: M 57
Constellation: Lyra


In summer 2018 I took the chance to revisit a showcase object in the constellation Lyra, which I took quite a couple of years ago. The night in August 2010 was less than suboptimal and my Schmidt-Cassegrain scope was not really fit for the purpose to obtain sharp pictures across the entire format of my DSLR camera. It is interesting that the outcome was still satisfying enough for posting it.

But after having optimized the collimation of my current 8" Ritchey-Cretien telescope back in 2017 and a thorough service of the mount earlier in 2018 I succeeded to obtain a perfect first light for my new Canon EOS700D camera. Eventually this was a late reconciliation with the object as I feel that what I got now was close to the optimum the equipment would yield. The picture you see is a 50% crop of the full frame at 1624mm focal length, so the apparent magnification is kind of a telescope with about 3.2 m focal length.

On top of the description about the beautiful planetary nebula explained in the page of my previous attempt there is some more detail in the current picture due to the exposure time of 1 1/2 hours, good resolution of the scope, and the excellent seeing in that night. So why not give it a a closer look and click at the image to obtain higher resolution? You may notice that the ring shows some knot-like structures. There is also some fuzzy nebulosity outside the ring's northern rim. Faint streaks go through the blueish part inside the ring. Additional stars apparently embedded at the right part of the nebula are not associated with the nebula at all. All of these features are much more prominent in professional pictures, but it fuelled my ambition to extract more information from the picture.

As the light from inonized Hydrogen is emitted in both the red and the green channel, but oxygen is only in green, I tried to isolate the red information in a separate channel on the one hand and subtract the red colour from the green on the other. I expected this procedure to reveal additional structure in the resulting black & white pictures, and yet it did:


Red channel


 


Red channel subtracted from green channel


 

On top of all that nice details, you should not forget to mind the fuzzy little smudge in the true-colour picture to the upper right of the nebula. This is the core of the faint background spiral galaxy IC 1296 more than 200 million light-years away...


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