PixInsight Processing Notes — Wizard Nebula (NGC 7380)

Optolong L-eNhance Filter on Seestar S30 Pro

SPCC Settings for Dual Band (L-eNhance)

• QE Curve: Ideal QE Curve (colour cameras have sensor QE baked into the Bayer filter)
• Narrowband Filters Mode: Tick this checkbox
  • Red channel: Wavelength 656.3nm, Bandwidth 10nm (Ha)
  • Green channel: Wavelength 500.7nm, Bandwidth 24nm (OIII)
  • Blue channel: Wavelength 500.7nm, Bandwidth 24nm (OIII)
• White Reference: Photon Flux (not Average Spiral Galaxy, better for emission nebulae)
• Optimize for Stars: Tick this (only available in narrowband mode, produces natural star colours)
• Background Neutralisation: Create a preview on a patch of pure background sky with no nebulosity, then select it as Region of Interest
• Catalog: Gaia DR3/SP
• Prerequisite: Image must be plate solved first via ImageSolver

Processing Workflow Order

1. Stack (WBPP or similar)
2. Crop
3. ImageSolver (plate solve)
4. DynamicBackgroundExtraction / ADBE / MGC (gradient removal)
5. SPCC (colour calibration with narrowband settings above)
6. Denoise here — Prism Deep OR NoiseXTerminator (not both)
7. Star removal (StarXTerminator / Zenith)
8. Stretch (GHS, HistogramTransformation, or MaskedStretch)
9. BlurXTerminator here (sharpening, after stretch, nonlinear stage)
10. SCNR (green removal, apply through a star mask to protect OIII)
11. Colour work (CurvesTransformation, ColorSaturation, NarrowbandNormalization)
12. Local contrast (LocalHistogramEqualization, HDRMultiscaleTransform)
13. Recombine stars (PixelMath screen blend)
14. Final adjustments (UnsharpMask, DarkStructureEnhance)

Key Rules

• Denoise in linear stage — before stretching and before star removal. The denoiser needs the full image with its natural noise distribution.
• Only use one AI denoiser — don’t stack Prism Deep and NoiseXTerminator on the same image. They do the same job and stacking them strips real signal.
• BlurXTerminator is not a denoiser — it’s a sharpener/deconvolver. Use it after stretching in the nonlinear stage. Can also run on stars layer separately with “correct only” mode.

SCNR (Green Removal on Stars)

• Process > ColorSpaces > SCNR
• Colour: Green
• Method: Average Neutral
• Amount: Start at 0.5–0.7 (not full 1.0)
• To protect OIII nebulosity: create a star mask first, then apply SCNR through that mask so only stars are affected

ADBE (Seti Astro Auto DBE) Settings for Nebulae

• Mode: Subtraction
• Smoothing Factor: ~0.5 (higher than default to avoid subtracting faint nebulosity)
• Samples per Row: 8–12 (fewer is safer with large nebulae)
• Sample Radius: 15–25 pixels
• Tolerance: Start at default
• Always inspect the extracted background model — if you see red or teal tones in it, the tool is pulling nebula signal. Increase smoothing or reduce sample points.

MultiscaleGradientCorrection (MGC) — PixInsight 1.9+

MGC uses real reference sky data (MARS database) instead of sample points to separate gradients from genuine signal. Much better at preserving faint nebulosity than DBE/ADBE.

Prerequisites

• PixInsight 1.9
• Gaia DR3/SP database files installed
• MARS database files downloaded (several GB)
• Image must be plate solved

Workflow with MGC

ImageSolver → SpectrophotometricFlux (SPFC) → MGC → SPCC

Key Settings

• Gradient Scale: 256 (good general purpose, corrects to corners)
• Structure Separation: 3 (default; reduce to 2 or 1 for better corner/edge correction)
• Model Smoothness: 1.0 (default; increase to 3.0–5.0 if wavy artefacts appear)

Why Use MGC

• Knows what the sky should look like from reference data
• Won’t accidentally subtract faint Ha/OIII extending beyond the obvious nebula
• One-pass results typically better than sample-point methods
• MARS has good coverage for northern targets like the Wizard (+58° dec)

SyQon Prism Deep — macOS Fix

If macOS Gatekeeper blocks the bundled Python framework:

# Strip quarantine flag
sudo xattr -rd com.apple.quarantine "/path/to/SyQon"

# Re-sign the Python framework with ad-hoc signature
codesign --force --deep --sign - "/path/to/SyQon/prism_cli/_internal/Python.framework"

# Re-sign the CLI executable
codesign --force --deep --sign - "/path/to/SyQon/prism_cli/prism_cli"

The sudo command will ask for your Mac password. No characters appear on screen while typing, but it is registering keystrokes.

Colour Work Tips for the Wizard

• Ha will dominate the red channel heavily; OIII will be subtle
• After SPCC, use SCNR to manage green cast (through star mask)
• Boost OIII (teal/blue) via CurvesTransformation or ColorSaturation targeting the cyan range
• NarrowbandNormalization can rebalance if Ha is overwhelming
• The drama in the Wizard is in the pillars and the cavity blown out by the central star cluster — LocalHistogramEqualization and HDRMultiscaleTransform bring these out
• DarkStructureEnhance deepens the dark lanes and pillars