NGC 7635 The Bubble Nebula

RGB data from 2012 

NGC7635 also called "Bubble Nebula" (Sharpless 162, Caldwell 11) is an emission nebula in the constellation Cassiopeia with a very particular "bubble" shape. It is 6 to 10 light years in size, and it was, created by the stellar wind from a central star (SAO 20575, BD+60 2522). 

NGC7635 was discovered by William Herschel in 1787 and its distance to us varies between 7100 and, 11000 light years, according to different sources.

I imaged this nebula in 2012 in RGB (with some Hydrogen alpha) and I am currently collecting exposure to make a new image of this nebula, in this case in full narrowband.

While waiting for enough narrowband data, and as I will in any case use the colour data from the first image for the stars in the new one, I have decided to entertain myself by reprocessing my 2012 image from scratch.

This reprocessing exercise has allowed me to see two facts: a) what poor processing I was producing back in 2012 😂😂 and b) how Pixinsight has evolved over the years and what new tools are available to us today.

Just to give an example, the use of WBPP (and within it, of course, LocalNormalization) has allowed me to use some exposures that I had discarded in 2012, obtaining final integrated images of the different channels with a resolution (measured by its FWHM) equal or even higher than the one I obtained at the time and certainly with a higher signal-to-noise ratio.

Other tools not used in 2012 and used now have been:

SpectrophotometricColorCalibration

GradientCorrection

BlurXTerminator (from Russell Croman)

LocalHistogramNormalization

Screen Stars script (from Mike Cranfield and Bill Blanshan)

The first image is the reprocessed (L)RGB version (that includes 8 sub-exposures initially discarded in 2012). The comparison with the 2012 image, below, I think is quite remarkable (link to the higher resolution version of the 2012 image here).

The third image is the new HaRGB version (which, in this case, includes 4 sub-exposures initially discarded in 2012). Here, again, the improvement is very substantial (link to the higher resolution version of the 2012 HaRGB image here).

All sub-exposures were taken in presential form from my observatory in Àger between August and October 2012, with Takahashi TOA-150 telescope and SBIG STL-11000M camera.

Updated 8/12/2024: Narrowband version

The last image is the new version of the nebula obtained with data remotely taken between September and November 2024, with Hydrogen alpha, Oxygen III and Sulphur II filters.

In total, this narrowband image accumulates 45 hours of exposure (stars are RGB).

For the processing of this image, I have used the new method described by Adam Block here.

Basically it consists of initially processing the image with an HOO palette and then inserting a colourised version of the SII image.

This is done using the Image Blend and NB Colour Mapper scripts from Mike Cranfield: many thanks to Adam and Mike for their continued contributions to astrophotographic processing with Pixinsight.

Click on the images for full resolution versions, or go to the Gallery section for complete exposure details.

Image processing: Pixinsight.

Observatory automation and remote operation with Talon6.