The Fossil Footprint, NGC 1491, an emission nebula in the constellation of Perseus, has been a challenge to capture and edit.  I started capturing this over a year ago but I could not get a result I was happy with from the data; I wanted to bring out some detail in the 'claws' of the footprint. This year I captured more data with a narrower dual filter and used new processing techniques. I created both SHO PIP and HOO PIP versions; I settled on a blend of the two as bringing out the most interesting detail and colour contrast.  There is very little Sii, just in the brightest part of the core, but abundant Oiii and Ha. It's about 10,700 light-years away, hence quite faint.

There is a small nebula having significant Oiii in the lower centre of the image; this is planetary nebula Ou 1, identified by Nicholas Outters as a possible PN in 2012, with more recent studies confirming that. There is also Sh2-209 nebula in the lower right.

Processing this was a bit problematic in that the Ha/Oiii data from last year was captured using the L-eXtreme filter and this year's was using the Antlia ALP-T filter. The narrower bandwidth of the ALP-T fools Normalise Scale Gradient into weighting them very low compared to the L-eXtreme subs - since the star flux from the wider filter is greater.  Running them all through NSG together and integrating them all together did not give me much more that the L-eXtreme stack on its own. To get around this I ran NSG on the L-eXtreme stack and then again on the ALP-T stack and then integrated the two stacks of weighted subs together. This gave weightings to each sub relative to the reference in each stack, so maintained higher weightings for the ALP-T subs.   

The Sii was captured using the R channel from an IDAS NB3 filter.  Stars are from a stack of short duration L-Pro subs.

I used the deconvoluted Ha as luminance for the LRGB recombination.