In Nov 2020 I started my first attempt to image the bubble nebula to celebrate the launch of my last satellite, with my camera at the time, a Kepler 4040. Now that I have a new camera, a Moravian C5A-100M, I decided it was time to try again.

This version does not yet have enough data and so is rather noisy, but it slipped below the horizon and is a project which will have to wait until much later in the year to complete. So this can be considered an interim version.

It's also the first time I have tried removing the stars at the earliest possible stage and processing stars and nebula separately, to be recombined at the end (using PixInsight's screen combine process in PixelMath). Though there is only narrow-band data here, I colour calibrated the stars using PixInsight's SpectrophotmetricColorCalibration process for narrow-band filters.

I have noticed a strange horizontal linear artefact about 40% up on the rights side. It's present in only 2 of the 3 filters and moves from sub-frame to sub-frame. I have no idea what it is and am still investigating.

The Bubble Nebula, NGC 7635, in the constellation of Cassiopeia, was discovered in 1787 by William Herschel. It is surprisingly far away, at a distance of more than 7000, and maybe as many as 11000  light years. The bubble is embedded in a region of ionised hydrogen (an HII region), which is energised by a hot, massive star within the bubble itself, causing it to emit light.

The bubble itself is the outer boundary of the powerful, high-speed "stellar wind" which is surging away from the surface of the super-hot star; as it slams into the cold gas in this region of space it heats it up, so hot that it becomes ionised and glows with emitted light.
This is a false-colour image with red showing light emitted by sulphur, green showing hydrogen emissions and blue showing the light emitted by oxygen, which dominates the hot shock front of the bubble's surface.

Also visible in this image, at the top right is part of the open cluster M52, and, at the top edge, about 30% across from the left the very unusual tubular planetary nebula PLN 112, which is rather closer than the Bubble Nebula at about 5200 light years.