Sh2-104 in Three Colour Palettes
 OHS Palette |
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 HaO3RGB |
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 Hubble Palette |
Click an image for full size version
December 21, 2025
Sh2-104 is a relatively small emission nebula in Cygnus. It fits nicely in the field of the 14″ SCT telsescope. It is also catalogued as DBW14 and lies about 14,000 light years away. It reminds me a little of the Rosette Nebula, but it is much smaller. It doesn’t seem to be a very p[opular target. That’s probably due to its small size and proximity to bigger and brighter targets, like the Crescent Nebula.
Tekkies:
Acquisition, focusing, and control of Paramount MX mount with N.I.N.A., TheSkyX. Guiding with PHD2. Primalucelab low-profile 2″ Essato focuser, ARCO rotator and Giotto flat panel. Equipment control with PrimaLuce Labs Eagle 4 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Average transparency and seeing. Acquired under a waxing crescent moon from June 28 – July 2, 2025. I captured the broadband data when the moon was less intrusive.
Celestron 14″ EDGE HD telescope at f/11 (3,931 mm focal length) and QHY600M-SBFL camera binned 2×2 with Optolong filters.
36x2m Red = 1hr12m
36x1m Green = 1hr12m
34x1m Blue = 1hr08m
50x5m S2 = 4hr10m
51x5m Ha = 4hr15m
49x5m O3 = 4hr05m
Total: 16hr02m
Preprocessing: The WeightedBatchPreProcessing script was used to perform calibration, cosmetic correction, weighting, registration, local normalization, integration, Drizzle integration, auto-cropping and plate solving.
Colour master: A colour master was made from the Red, Green and Blue masters using ChannelCombination in RGB mode.
Gradient Removal: DynamicBackgroundExtraction was applied to the RGB and narrowband masters.
Colour Calibration: ColorCalibration was used to calibrate the RGB master.
Deconvolution: BlurXterminator was used on the RGB and narrowband masters with Automatic psf at default settings.
Linear Noise Reduction: NoiseXterminator was applied to the RGB and narrowband masters with settings Amount=0.9 and Iterations=3
Star Removal: StarXterminator was used to remove the stars from each of the RGB and narrowband masters, with default settings. Only the RGB stars-only image was preserved.
Hubble Palette Image Creation: The three narrowband masters were combined using ChannelCombination in RGB mode assigning S to red, H to green, and O to blue.
Stretching: HistogramTransformation was applied to the RGB, SHO and narrowband masters to make pleasing images. Approximate background level after the stretches was 0.10 for RGB and SHO and 0.09 for the individual narrowband masters.
Nonlinear Processing
OHS Image Creation:The three stretched narrowband masters were combined using ChannelCombination in RGB mode assigning O to red, H to green, and S to blue.
Background Cleanup: Artifacts that were visible in the three master colour images were removed using the CloneStamp tool.
Nonlinear Noise Reduction: NoiseXterminator was used to reduce noise in the background areas of the RGB, Hubble and OHS masters with settings Amount=0.9 and Iterations = 3
Dynamic Range Compression: The CreateHDRImage script was used to compress the core of the nebula using a mask made with the RangeSelection tool. This was applied to all three images.
Contrast Enhancement: LocalHistogramEqualization was applied twice to each image. A Contrast Limit of 1.5 and 1 iteration was used for each LHE application (scale 150, strength 0.35; scale 50, strength 0.22).
Sharpening: A mask was used to select brighter regions of nebulosity in each image for sharpening with MultiscaleMedianTransform (Layers 2 – 43with strengths of 0.07, 0.05 , 0.03 and 0.03, respectively).
Hubble Palette and OHS Colour Adjustments: CurvesTransformation was used with the Hue tool to adjust the colour tones in the two narrowband images.
Star Processing and Restoration: HistogramTransformation was used to stretch the stars-only RGB image, followed by CurvesTransformation through a star mask to boost saturation using the Saturation slider. The stars were added back into the three master images using the PixelMath expression combine(starless, stars, op_screen()).
Final Steps: Background, nebula and star brightness, contrast and saturation were adjusted using several iterations of CurvesTransformation, with masks, as required. ICCProfileTransformation (sRGB IEC61966-2.1; Relative Colorimetric with black point compensation) was applied prior to saving as a jpg.
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