The Ring Nebula, M57, is a familiar object to most amateur astronomers. It is a compact ring in the constellation Lyra. If asked for an adjective to describe it I might use the word “tidy”. It seemed to have well-defined boundaries unlike most of the nebulae we look at which just tend to become more diffuse and not have clear edges.
I was surprised when I took the first hydrogen alpha sub exposures on this and saw this diffuse, faint outer ring. I quickly sent an screenshot to one of my imaging partners on this system asking him if he knew there was an outer ring on the ring. Old pro that he is, he replied, “yes, it’s a cool feature.” Meanwhile, I was bouncing in my chair chanting “outer ring!”. I’m sure my spouse would have been concerned if she’d been awake to witness this behavior.
M57 was actually the first image I did with my SV80 refractor. It was very tiny that field of view and even in this 14 inch Planewave’s 2500mm focal length, the Ring is a small target, but the lure of the outer ring was too much to resist.
I decided to get data in all three narrowband filters though most people only bother for h-alpha and oxygen. With that combination you can produce an HOO image that approximates natural color. However, the sulfur signal was strong enough that I wanted to see what it would produce. As it turned out, the sulfur signal was low enough compared to the much stronger hydrogen and oxygen that it gets lost in the mix so that’s likely why most people only bother with H and O.
From the moment I saw the initial subs I had this idea in my head of how I wanted to present the image. It turned out to be quite a challenge to realize. This was my third full processing attempt but in each attempt there were numerous false starts that led to me backing up and trying different paths. All together I probably spent 15-20 hours on processing this.. The final result comes the closest to my vision. To truly do that outer ring justice probably needs at least double and maybe triple the 20 hours of acquisition time I got.
This turned out to be the most complex processing I’ve ever attempted and it pushed my skills to (and really beyond) my limits. I don’t think I realized everything that could be gained from the data but I’m pretty happy with the results. Thanks to those on the NOVAC imaging hangout who provided suggestions and advice along the way!