I've shot tons of PNs over the years, but for some reason never got around to this one. Too many galaxies, I guess. The OIII halo here was a surprise to me, although now that I look around I see plenty of images with it. There's some Ha in the halo as well, but it's extremely faint compared to the OIII. This is 24 hours of bicolor with a C11 and SXVR-H694 at 0.84 arcsecs/pixel under Bortle 8 skies. Thank goodness for narrowband filters.
I did two stretches on this, the first for the core and the second for the halo. In the latter image, the core was of course seriously blown out. I used the Pinch tool in Photoshop to pinch the core down to nothingness, then used Pixinsight's max operator in PixelMath to blend the core and halo images. It seems to have worked out well, but in etrospect I wonder if I could have removed the blown out core with Morphological Transform in PI.
Full resolution image, with details of capture and processing, are at the link.