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So if I understood that, the latest image is Ha-G (with scaling) and is an attempt to keep only emission Ha without the contribution from so many stars? The spiral in the core certainly is news to me. Some interesting stuff you're coming out with here, particularly for such an otherwise well known object.

If you're not short on objects to capture, that's gotta be worth a try on others too!

Edit: ok, the filename gave it away a bit. Random thought occurs, is the average really "green"? Would subtracting other channels, for example, L instead work better?

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Canon DSLRs: 7D, 5D2, 1D, 600D, 450D full spectrum, 300D IR mod
Lenses: EF 35/2, 50/1.8, 85/1.8, 135/2+SF, 28-80 V, 70-300L, 100-400L, TS-E 24/3.5L, MP-E 65, EF-S 15-85 IS
3rd party: Zeiss 2/50 makro, Samyang 8mm fisheye, Sigma 150 macro, 120-300 f/2.8 OS, Celestron 1325/13
Tinies: Sony HX9V.

Hi popo,

I still haven't got around to capturing separate luminance subs so I synthesise by combining RGB. My reason for subtracting green was my assumption that it's the only channel I can be reasonably sure has no significant contribution from hydrogen emission. In a perfect world I'd get a narrowband continuum filter just off from the Hα line (they are available) and subtract that data but as I'll eventually be recombining the Hα with the rest of the data, albeit boosted and with a suitable colour, I think Hα - Green/15 will be good enough.

BTW, I've just discovered that spiral structure in the bulge is also visible if one uses a PixInsight Star Mask (Harry's tutorial explain how) and then do some HDR Multiscale Processing on the luminance image.

OK, that's me done with PI for the day. Processing is going quite well but I think my attention level has peaked!

Bob.

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OM-D E-M5 + ED 12-50mm, H-PS14042E, H-F007014E, L-RS014150E, M.ZUIKO DIGITAL 45mm 1:1.8.
Gitzo GT1541T, Arca-Swiss Z1 DP ball-head.
Astrophotography: TEC 140 'scope, FLI ML16803 camera, ASA DDM60 Pro mount.