Dear all, it is a while I am absent from this forum, unfortunately lately have less and less time to spend for this hobby and in particular processing new images
I collected during last months lots of light on a very particular object, the probable aftermath of the explosion of a supernova in 185 AD, event recorded by Chinese astronomers as the appearance of a new star in the Nanmen asterism (a part of the sky identified with Alpha and Beta Centauri on modern star charts). This is thought to be the earliest recorded supernova.
Usually referred to as RCW 86, this SNR has a relatively large angular size of roughly 45 arc minutes but it is extremely faint, so much that there are apparently no amateur images and very rare professional images recording the whole remnant. In particular I was able to mostly find infrared and radio images taken from space showing the SNR shell and only one professional ground image recording the faint filaments in Ha using a 2 meter class telescope.
Processing this one was a real challenge since even once the long Ha stack (17 hours) was heavily stretched the relatively crowded field made almost impossible to discern the filaments. To overcome this I had to subtract the continuum (the red filtered image opportunely stretched to match the star sizes) and add the result to the conventional RGB base. Same was required for the OIII (8 hours). Some tweaks on the stack (adding again low stretch Ha & OIII) and here is the result:
Ancient Supernova SN185
It was a difficult task but I am quite happy with the overall look, not to mention to have something probably unique (to my knowledge).
I hope you will like it. Other details on the object and imaging data on my website.
Clear skies
Marco
I imagine it was outside your normal processing approach but that you kept at it, trying different things and in the end you have come up with a very special image, congratulations 
Looking at this image reminds me why I pushed to have Mark Bolton get you down for AAIC his year, hopefully you will get an invite in two years and I am sure we will all flock to hear how you do your magic..... and I will give you a big hug 
