Sh2-132, the Lion Nebula
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November 2, 2025
Sh2-132 is sometimes called the Lion Nebula. It is a large complex cloud of glowing gas in southern Cepheus near the border of Lacerta. It lies about 10,400 light years away in the Perseus Arm of our galaxy, the Milky Way. The visibile structures come mainly from the emissions of ionized sulfur, hydrogen and oxygen atoms. This image was captured using narrowband filters that isolate these wavelengths, and was processecd in two palettes to show the different gases in the nebula.
Tekkies:
Acquisition, focusing, and control of Paramount MX mount and other equipment with N.I.N.A. and TheSkyX. Unguided. Focus with Primalucelab Sesto Senso 3 on the Sky-Watcher stock focuser. Equipment control with Primalucelab Eagle 4 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph under average transparency and seeing and a nearly full Moon from October 2 – 10, 2025.
Sky-Watcher Esprit 70 EDX refractor, QHY367C Pro camera.
L-Synergy Filter: 193 x 5m = 16hr 05m
L-eXtreme Filter: 172 x 5m = 14hr 20m
Total: 30hr 25m
Preprocessing: The WeightedBatchPreProcessing script was used to perform calibration, cosmetic correction, weighting, registration, local normalization, integration and Drizzle integration of all frames (Fast Drizzle, Scale=2x, Drop Shrink=0.9).
Gradient Removal: DynamicBackgroundExtraction was applied to the two masters (L-Synergy = SOO; L-eXtreme = HOO).
SHO Master Creation: The DBExtract script was use to create S, H and O masters from HOO and SOO. The S, H, and O were combined using ChannelCombination with S assigned to red, H to green and O to blue.
Deconvolution: BlurXterminator was applied to the SHO image using an automatic PSF, star sharpening set to 0.50, and non-stellar sharpening set to 0.9.
Linear Noise Reduction: NoiseXterminator was applied with Amount=0.95 and Detail=0.5
Stretching: HistogramTransformation was applied to make a pleasing yet bright image. Approximate background level after stretch was 0.10
Nonlinear Processing
Star Removal: StarXterminator was used to remove the stars, with Unscreen selected.
Nonlinear Noise Reduction: NoiseXterminator was applied with Amount=0.9 and Detail=0.25
Contrast Enhancement: HistogramTransformation was used to adjust brightness and black point. LocalHistogramEqualization was applied twice. A Contrast Limit of 1.5 and 1 iteration was used for each LHE application (scale 40, strength 0.25; scale 150, strength 0.28). ExponentialTransformation was applied.
Sharpening: A mask that selected just the brightest parts of the nebula was used with MultiscaleMedianTransform to sharpen Layers 2 – 5 with strengths of 0.03, 0.03, 0.03, and 0.02, respectively.
Foraxx Palette Image Creation: The S, H and O channels were extracted from the SHO starless image and recombined using the Foraxx Palette Utility script.
Contrast, Brightness and Colour Adjustment: Brightness, contrast, hue, and saturation of both images were adjusted in several iterations using CurvesTransformation and ExponentialTransformation, with masks as required.
Star-only Processing: Magenta stars were corrected in three steps. 1) The stars-only image was inverted. 2) SCNR was applied. 3) The image was inverted back to its original state. The lightness was extracted from the stars-only image and used to make a mask. Colour in the stars was boosted through the mask with two applications of CurvesTransformation’s Saturation tool.
Star Restoration: PixelMath was used to insert the stars back into both starless images using the following expression:
combine(starless, stars, 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 image was downsampled to the original resolution for sharing on this website.
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