Weak (and amazing) supernova remnant, Sh 2-224

In November and December of 2016 I took a total of 15.5 hours of exposure, with a single filter (H-alpha), of Sharpless 2-224, a supernova remnant (SNR) in Auriga, the weakest object I have tried so far. This is extremely weak. Even with so much time for a monochrome image, what comes out is still very weak (I am insisting,  yes) and I had to stretch the image's histogram like never before. Maybe I shouldn't have stretched it so much, but I didn't want to left any trace of signal in the dark. Maybe I'll come back to it and add more data in H-alpha.

Telescope: Astro-Physics 130GT

Filter: H-alpha, Astrodon 5nm

Mount: ASA DDM60pro

Maxim DL, Pixinsight

93 frames of 600s each, some with gibous moon up

I have not seen many photos of this object in the web, either. The best is probably by Dean Salman:

http://sharplesscatalog.com/narrowband.aspx

Here a version in H-alpha + SII by Rolf Sveinhaug:

https://www.astrobin.com/63478/

I think it is a beautiful object anyway. The catalog name is SNR G166.1 +4.4

Some data.  It is located at 4.1 kpc (kiloparsecs) of distance, and measures, at this moment, about 58,4 parsecs of diameter. Seems to be about 81000 years old. It emits mostly in H-alpha and radio frequencies, but there is enough signal at other emission lines like OIII and SII to allow for multifilter false-color renditions like the ones mentioned above. My intention is to make the OIII version, even though it will be painful to invest more than 10 hours, perhaps 15, of clear nights in frames that apparently have close to zero signal. But that's the name of the game.

It has been suggested that the peculiar shape of this SNR (described as an almost complete circular shell with a wing) is "the result of a single SNR evolving in two regions of sharply different densities, or of two successsive SNR's" [Huang Y-L, Thaddeus P, Astrophysical Journal, 309, p804-821 (1986)]. Huang and Thaddeus (1986) also conclude that type II supernova are associated to large clouds of ionized hydrogen, from which the progenitors of these SN were born as massive and energetic stars. In fact, not far from SNR G166.1 +4.4 there another SNR, OA 184, which also seems to be associated to the large hydrogen cloud in teh area.

The name supernova "remnant" sounds a bit negative to me. I'd say that it is not a remnant, it is the next step in the evolution of matter in the Universe: from a huge and cold hydrogen nebula, to a stellar protodisk, to a star, to a supernova, to a maravelous shell of new, fresh heavy chemical elements that expands quickly and spreads that side of the cosmos with them... which eventually will again coalesce in the next generation of stars and planets, and perhaps people that write about the Universe. On the other hand, these "remnants" are beautiful, and inspiring, aren't they?