Final Non-Linear Processing

Introduction

At this stage, your image is fully stretched, colour-calibrated, and balanced. Now comes the delicate art of final non-linear processing — the last adjustments that transform a good image into a truly great one.

The goal is to enhance detail and depth without overprocessing or introducing artefacts.

1️⃣ Subtle Sharpening

• Where: MultiscaleLinearTransform or UnsharpMask
• Use a light touch
• Protect stars/background with masks

MLT:

• Enable first 3–4 layers
• Bias: 0.05–0.1

Unsharp Mask:

• StdDev: 1.0–1.5
• Amount: 0.3–0.4

📷 [MLT + Unsharp Mask screenshots]

💡 Tip: Always compare at 100% zoom.

2️⃣ Gentle Noise Reduction

• Apply second pass with NoiseXterminator
• Strength: 0.2–0.3
• Use masks to protect detail

📷 [NoiseXterminator screenshot]

💡 Tip: Apply on starless layer if possible.

3️⃣ Star Integration Touch-Up

• Inspect star + starless layers
• Recombine using PixelMath
• Optional slight blur on stars

📷 [PixelMath recombination]

💡 Note: Mismatched colour or stretch can cause halos or shifts.

4️⃣ Subtle LHE Pass

• Where: LocalHistogramEqualization
• Kernel: 30–40
• Contrast: ~1.2
• Use masks or starless image

📷 [LHE screenshots]

💡 Adds micro-contrast and depth.

5️⃣ Final Colour Balancing

• RGB/K: S-curve
• Channels: fine colour balance
• Saturation: subtle boost
• Lightness: fine contrast

📷 [CurvesTransformation screenshot]

💡 Art vs Science: Use references, but allow artistic interpretation.

6️⃣ Inspect at 100%

• Check star shapes
• Look for artefacts
• Ensure natural detail

📷 [100% zoom check]

💡 Tip: Step away and revisit with fresh eyes.

✅ Quick Checklist

• Subtle sharpening applied
• Noise reduced carefully
• Stars recombined cleanly
• Third LHE pass applied
• Colour balanced
• No artefacts at 100%

Next Step

Your image is now ready for export and sharing.

Next: Saving for Success — Exporting Your Astrophotography Images the Right Way