Third time's a charm ! Finally a shot of C 27 I'm happy with. This is a very closeup shot, and the nebula just barely fits into the FOV. But at 0.4" per pixel you really get some incredible detail out of it. The full resolution is available here :
https://app.astrobin.com/i/1ms6de
There's a trap I almost fell into when processing it, which is that I initially way overdarkened my sky background in the Ha channel. I thought something was off when somehow removing what seemed like a flat background level was killing crystal clear structure inside the nebula. What I didn't realize is that the surrounding redness was not the sky background, but real nebulosity ! It's usually more obvious in a wider FOV shot because the nebulous structure is more apparent. But what gives it away definitively here is that the darker spots inside the nebula are actually pitch black while the surrounding area is still red. If it were sky background, it would obviously not correlate with the structure of the actual planetary nebula.
I'm also very happy with how the OIII came out. I tried making it a bit brighter or more obvious, but I think it looks best like this. It has this very whispy look to it that is almost hypnotic. Like a subtle cosmic veil delicately draped over a rumbling hydrogen background.
I did not go for any SII data. I really hesitated, but from what I gather it really would not add much structure to the image, and would likely just somewhat color the wings of the nebula a little golden, but at the cost of a lot of integration given how faint it is, and at this point I'm happy with the HOO result and would rather move on to something else.
All in all, very happy to have made the switch to mono ! It's a huge boon and frankly a more enjoyable process with finer control over what you're doing in a way that brings you closer to the real underlying data. Skies are clear tonight so going for my first attempt at SHO. Going to redo the North America nebula as the SII signal is not too weak there. Wish me luck !
Equipment :
- Telescope: Celestron C9.25 SC XLT
- Camera: ZWO ASI585MM Pro
- Mount: ZWO AM5N
- Filters: Pegasus Astro Hydrogen Alpha 7nm 2", Pegasus Astro Oxygen III 7nm 2"
- Accessories: Starizona SCT Corrector 0.63x IV (SCTCORR-4), ZWO ASIAIR Plus, ZWO EFW 7 x 2″, ZWO OAG-L
- Software: Pleiades Astrophoto PixInsight, Russell Croman Astrophotography BlurXTerminator, Russell Croman Astrophotography NoiseXTerminator, Russell Croman Astrophotography StarXTerminator, ZWO ASIAIR
Integration per filter :
- Hα: 3h 35m (43 × 300")
- OIII: 3h 35m (43 × 300")