NGC 1491 (SH2-206) is an HII region, an emission nebula on the edge of a vast cloud of neutral gas, about 11,000 light-years away in the Perseus arm of our own Milky Way Galaxy. It has been called the Fossil Footprint Nebula, and indeed, perhaps one can imagine a 3-toed dinosaur print. 

The 11th magnitude blue-white O5 star BD+50 866, ionizes the gas around it with its UV radiation, creating the HII region. The shock front is just below the bright O5 star, blowing a half bubble, showing in this image as a bluish arc. This front is the product of high speed, gas outflows that collide with the slower moving gas around it. Further from the O5 star the gas slows down as it expands into the surrounding non-ionized hydrogen, forming the ionization front, the dividing line between ionized and non-ionized gas. The folded arcs of gas along the ionization front  show up here as reddish-orange, and is marked by many globules, including an elephant trunk directly below the O5 star and pointed toward it. These structures are likely dense neutral gas, that are surrounded by ionized gas, creating  the brightest structures in the nebula. More details can be found in this scientific paper.

My Processing: 
All raw image files were calibrated, registered and stacked using DeepSkyStacker. The SHO image was composed in StarTools, with background extraction, digital development, HDR, and deconvolution. In the color module an SHO blend was used: 20SII+80Ha,20Ha+80OIII,100OIII. The RGB image was also processed separately in StarTools to use for the stars.

In PhotoShop a starless version of the SHO stack was made with StarXterminator, followed by the APF-R multi-scale unsharp mask (as used by NASA). Color adjustments were the standard Cyan-Yellow, Y to Gold, Gold to Red. A little curves was added to brighten the core, and individual +/-  saturation adjustments were made to each color (RYGBCyM). My goal was to bring out all the individual colors that were present in the image and try to balance them out. The RGB stars were added using Screen mode. Both layers had noise reduce/sharpened with  NoiseXterminator.  Final color balance and levels adjustments finished off the processing.

RASC Data:
Date: 2021 December - 2022 January
Narrowband: 33.5 hours, RGB: 45 minutes
Narrowband Ha, OIII, SII: 12 h, 11 h, 10.5 h, with frames of 1,800 s each 1x1
RGB (Star Colour): 5 x 180 s each 1x1
Flats, Biases (used as Flat Darks) and Darks
Sierra Remote Observatories, Auberry, California
RCOS 16" f/8.9 (3550mm focal length)
CCD Camera SBIG STX16803 16MP (4096 x 4096)
Paramount ME mount
Filters are SBIG RGB, Ha (7nm), OIII (8.5nm), SII (8nm)