Pacman Nebula Wide Field in SHO

Foraxx Palette	OHS Combination
Simulated Natural Colour	Hubble Palette

Click images above for full size versions

September 27, 2025

NGC 281 is known as the Pacman Nebula. This nickname comes from its appearance, resembling an early video game character. The designation NGC 281 refers to the nebula; the star cluster in the centre is IC 1590. These cluster stars were born out of this hydrogen gas, and now cause it to glow. The black, dense globules are called Bok globules, from which the bright stars are born. The Pacman is about 9,500 light years away, and covers a little more sky than the full Moon. This object was my First Light target for the Sky-Watcher Esprit 120 telescope used for this set of images. That image used a broadband filter for a natural-colour image. This image set was made with two dual-band narrowband filters: the Optolong L-Synergy and L-eXtreme.

Tekkies:
Acquisition, focusing, and control of Sky-Watcher Wave 150i mount and other equipment with N.I.N.A. and Green Swamp Server. Guided with PHD2 using a Sky-Watcher 50mm EDX guide scope and QHY5 II L guide camera. Focus/rotation with Primalucelab 3″ ESATTO/ARCO. Equipment control with Primalucelab Eagle 6 Pro computer. All pre-processing and processing in PixInsight. Acquired from my SkyShed in Guelph. Acquired under average transparency and seeing and little to no moonlight from September 8 to 19, 2025.

Sky-Watcher Esprit 120 refractor, QHY168C Pro camera, Optolong filters

L-Synergy Filter: 181 x 5m = 15hr 05m
L-eXtreme Filter: 168 x 5m = 14hr 00m

Total: 29hr 05m

Image scale 1.15 arcsec per pixel

Finder Chart:

Data Reduction and Linear Processing

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, OHS Combination, and Simulated Natural-Colour Image Creation: The S, H and O channels were extracted from the SHO starless image and combined using the PerfectPalettePicker script.

Hubble Palette, OHS Combination, Foraxx Palette and Simulated Natural-Colour Image Adjustments: CurvesTransformation was used to adjust the colour tones in all of the starless images.

Contrast, Brightness and Colour Adjustment: Brightness, contrast, hue, and saturation were adjusted in several iterations using CurvesTransformation, ExponentialTransformation and the Jurgen Terpe Selective Color Correction script, 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 sizes were reduced slightly with the StarReduction script.

Star Restoration: PixelMath expression combine(starless, stars, op_screen()) was used to combine the starless and stars-only images.

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.