Crescent and Soap Bubble Nebulae

Click image for full size version (22 MB)

July 11, 2026

Space.com Best of 2018 - Crescent and Soap Bubble

The Crescent Nebula is an emission nebula situated about 5,000 light years away, and dominates the right side of this image. It lies in a patch of Milky Way that runs right through Cygnus, the Swan. The richness of the Milky Way in this region is apparent from the vast number of stars in this image. The red hues of the Crescent Nebula and the surrounding area is due mostly to glowing hydrogen gas; the teal comes from emissions of oxygen atoms. The Crescent Nebula is being energized and “blown out” by energetic winds coming from the powerful central star, WR136. The WR signifies that it is a ‘Wolf-Rayet’ star. These stars are very hot, at least 20 times the mass of the sun, and losing mass rapidly. I read that WR136 is shedding the equivalent of the Sun’s mass every 10,000 years and that it will eventually explode in a supernova. That will probably produce another very interesting nebula for our descendants to look at.

Another amazing object in this image is to the upper-right of centre: the ghostly Soap Bubble Nebula. It was discovered in 2007 by amateur astronomer Dave Jurasevich using a 160 mm refractor. I first imaged this field in 2018 (see inset image). The current image goes much, much deeper. It’s amazing how the equipment, softare, and my processing skills have changed over the years. Check the annotated image to identify some of the other nebulae, both bright and dark, in this field.

This image is a collaboration with Steve Barnes, who has been imaging the skies in both hemispheres for decades. Each of us acquired data independently and I processed the 42hr 35m of data as described beolow. 

Tekkies:
Ron’s Data
Acquisition, focusing, and control of Sky-Watcher Wave 150i mount and other equipment with N.I.N.A. and Green Swamp Server. Primalucelab 3″ ESATTO focuser, ARCO rotator, GIOTTO flat panel and ALTO cover motor. Player One Xena-M guide camera, OAG and Filter Drawer MAX. Equipment control with Primalucelab EAGLE 6 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Acquired under above-average transparency and seeing and variable moonlight from June 22 to July 2, 2026.

Sky-Watcher Esprit 120, Player One Poseidon-C Pro camera, Optolong L-Quad Enhance filter and L-eXtreme filter.

LQUAD       86 x 5m = 7hr 10m
L-eXtreme  118 x 5m =   9hr 50m

Ron’s Total = 17hr 00m

Steve’s Data
Celestron C11 with HyperStar v3, ZWO ASI2600MC Air OSC camera and Sky-Watcher EQ6 Pro mount.
Acquired from Benmillar, Ontario during June and July 2026.

Svbony SV220 DUO filter: 247 x 5m = 20hr 35m
Luminance filter: 60 x 5m = 5hr 00m

Steve’s Total: 25hr 35m

TOTAL EXPOSURE TIME:  42hr 35m

Image scale 0.45 arcsec per pixel (based on Ron’s 2x-drizzled data)
 
 
Finder Chart and Annotated Image:
 
 
 
Data Reduction and Linear Processing

Preprocessing: The WeightedBatchPreProcessing script was used to perform calibration, cosmetic correction, weighting, registration, integration and drizzle integration (2X). StarAlignment was used to align Steve’s two masters to Ron’s masters. The four images were then cropped identically. 

Master Images: A master Ha image was made by averaging the red channels of the two narrowband masters. A master O3 image was made by averaging the green and blue channels from the two narrowband masters. A master broadband image was made by averaging the two broadband master images, and is referred to below as RGB.

Gradient Removal: DynamicBackgroundExtraction was applied to the RGB master.

Colour Calibration: BlurXterminator was applied to the RGB master with Correct Only selected, followed by ColorCalibration.

Deconvolution: BlurXterminator was applied to the RGB and narrowband masters with Automatic psf , star sharpening set to 0.5, and non-stellar set to 0.9. 

Narrowband Star Removal: The stars were removed from both narrowband masters with StarXterminator. The stars-only images were discarded.

Stretching:  MultiscaleAdaptiveStretch was applied to make pleasing images from the RGB and narrowband masters. Approximate background level after the stretch was 0.1.

Nonlinear Processing

Initial Noise Reduction: NoiseXterminator was applied to all three masters with settings Amount=0.9 and Interations=4.

Star Removal and processing:  StarXterminator was used to remove the stars from the RGB master with Unscreen checked. Colour was increased in the stars-only image by increasing saturation using CurvesTransformation through a star mask. SCNR was applied to remove a hint of green in the stars-only image.

Supplemental Stretch: HistogramTransformation was used to darken the black point and brighten the image overall.

Initial Saturation Boost: CurvesTransformation’s saturation tool was used to boost colour in the starless RGB image. A range mask made with RangeSelection was used to protect the background.

Narrowband Blending: The intital addition of Ha was completed using Jurgen Terpe’s CombineHaWithRGB script, followed by CombineRGBandNarrowband script to add O3 and further Ha.

Secondary Noise Reduction: NoiseXterminator was applied to the HaO3RGB image with settings Amount=0.9 and Iterations=5. 

Contrast Enhancement: The CreateHDRImage script was applied with Layers=7 and strength of 0.25, with intensity checked. LocalHistogramEqualization was then applied twice. A Contrast Limit of 1.5 and 1 iteration was used for each application (scale 150, strength 0.18, and scale 40, strength 0.19). 

Sharpening: BlurXterminator was applied (no star reduction, no halo reduction, manual psf=3, amount = 0.1). Bill Blanshan and Mike Cranfield’s Star Reduction script was used to slightly shrink brighter stars.

Star Restoration: Stars were added back into the image using the PixelMath expression combine(starless, stars_only, op_screen())

Final Steps: Background, nebula, and star brightness, contrast, and saturation were adjusted in several iterations using CurvesTransformation with masks as required. ICCProfileTransformation (sRGB IEC61966-2.1; Relative Colorimetric with black point compensation) was applied prior to saving as a jpg. The finder chart was made using the FindingChart process. The annotated image was made with the AnnotateImage script.