📄 Original output of the script. The unedited todo.md that Svenesis ImageMono Train wrote alongside the report – the hand-work that follows, with the exact menu paths in Siril.
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🎨 Final Processing — M 16 (HOO)
Everything the script produced is linear and colour-calibrated. The steps below are the creative, non-linear part — they're yours to taste. Do them in Siril (or PixInsight / Photoshop / Affinity Photo).
💡 Work on a copy, and keep the linear masters in masters/ so you can always redo from any step.
📖 New to this? The three stages are always: (1) flatten the background → (2) calibrate colour (already done for you) → (3) stretch, and only then the artistic touches. Stretching before calibrating ruins the colour, which is why the script hands the image over still linear.
Narrowband (open M_16_HOO.fit)
- Starting point. The channels were already normalized to Ha, so the image is balanced — not the pure-green you'd get from a raw SHO combine.
- Background check (optional) — Image Processing → Background Extraction (degree 1) if a gradient remains.
- The channels were additionally colour-calibrated with SPCC in narrowband mode, using each line's wavelength — so the starting balance is physical, not just normalized. ⚠️ But the channels were also normalized to Ha first, which flattens the very line ratio SPCC then measured — so treat this baseline as approximate, and see the note in
output.mdfor which of the two to switch off.
- The channels were additionally colour-calibrated with SPCC in narrowband mode, using each line's wavelength — so the starting balance is physical, not just normalized. ⚠️ But the channels were also normalized to Ha first, which flattens the very line ratio SPCC then measured — so treat this baseline as approximate, and see the note in
- Stretch. Histogram or GHS. Keep the background neutral and dark.
- Colour balance to the look you want (the classic Hubble gold/teal): per-channel Curves, or Siril's colour tools. A little goes a long way.
- SCNR (remove green) again if a green cast or green stars reappear after stretching.
- Denoise — narrowband is noisier than broadband — then boost saturation for the vivid emission-line colours.
- Star reduction (recommended) — SHO stars look best small; or replace them with round RGB stars for natural colours.
- Final contrast / curves, crop the borders.
- Export a 16-bit TIFF or PNG.
Tips
- A separate broadband RGB run gives you natural star colours to blend over the narrowband nebula.
- The filters this palette skipped were never stacked, so another palette needs a full re-run — untick Stack only the filters this palette uses first.
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