This is data from the end of August. I wanted to add another session but the clouds haven't cooperated beyond one slot of about 4 hours. I took HS and O but processed as HOO and then changed the hue to blue; this matches the RCB colors.
The Cygnus loop is, of course, a supernova remnant left over from a massive stellar explosion. The most recent estimate when the supernova occurred is 21,000 years ago but estimates have varied to as low as 5,000 years [1,2,3]. It is located in the plane of the Milky Way and is 2,600 ly from earth; currently it has a diameter of around 130 ly and is still expanding.
NB images bring out the colors of the glowing clouds of gases, largely excited by the compression wave from the explosion [2,3] but RGB images show that there is also considerable interstellar dust and debris. The dark background of the NB images is also slightly misleading since, as would be expected since the loop lies in the plane of the Milky Way, the background is a dense star field, again visible in RGB images.
Of course all images only show what they can; [4] shows in interesting composite image containing X-ray data that shows huge structures that are invisible to optical systems.
[1] https://www.nasa.gov/mission_pages/galex/pia15415.html
[2] https://www.nasa.gov/multimedia/imagegallery/image_feature_688.html[3] https://en.wikipedia.org/wiki/Cygnus_Loop
[4] https://scitechdaily.com/astronomers-determine-the-distance-of-the-cygnus-loop/
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