Centaurus A is a fascinating galaxy gracing the skies of the Southern Hemisphere and is of course located in the constellation of Centaurus. It is ~ 12 million light years away and about 60,000 light years across, although I imagine that when calculating its size, choosing where the galaxy starts and finishes was a matter of some conjecture. I recently saw it visually through a 17" Dobsonian and the spectacular dust lane is remarkable to see through the ocular. Clearly there is a lot going on here and it is believed to be the result of the collision and merger of two galaxies. It has a super massive black hole of 55 million solar masses at the centre which is spewing out two relativistic jets. As these collide with hydrogen clouds they energise them resulting in a Ha glow, which is very apparent on the north side through the Ha Narrow Band filter. The image is north up.
In processing this image I used the Continuum Mapping process to subtract the Red light signal from the Ha. After doing so, it was clear to me that there is a large signal from knots of gas in and around the dust lane but more broadly right through the core of the galaxy. I decided that since this Ha signal is clearly there I would allow a subtle addition to permeate the core, thus the warm pink/ red appearance. The Ha glow from the relativistic jets was also clear to see and came through nicely in the image.
I got much more signal in this image than I did back in 2021 when I last imaged it and it is amazing to see here the large number of concentric shells of stars emanating out from the centre. This was most obvious in the starless image during processing. I must admit I was suprised that this C11 image has captured so much more than the 2021 image which was capture on my C14. The C14 image has a smaller FOV and a somewhat smaller image scale (0.47 "/pxl vs 0.67"/pxl). This image has 28 hrs integration versus 23 hours for the 2021 image.  

Interestingly on a like for like basis the C11 has a 20% higher photon flux and 10% higher SNR than the C14, despite the smaller mirror, and this is the dominating effect of the shorter focal length. The extra integration time means that I captured 45% more photons and a 20% higher SNR in 2023 versus 2021. Is that sufficient to explain the apparent huge difference in SNR? Frankly I don't know.

Version B is a cropped in view and accessible via the mouse over.