My HOO processing workflow in PixInsight

Here’s a breakdown of the exact process I follow in PixInsight when processing narrowband data for HOO specifically.

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1. Process RGB Channels (for RGB Stars)

I like getting natural star colors by processing separate RGB subframe stacks first:

• DBE: Run Dynamic Background Extraction on Red, Green, Blue -> Red_DBE, Green_DBE, Blue_DBE

• LRGB Combine: Combine Red_DBE, Green_DBE, Blue_DBE -> RGB

• SPCC: Run Spectrophotometric Color Calibration on RGB -> RGB_Calibrated

• StarXTerminator: Run StarXTerminator on RGB_Calibrated -> RGB_Starless, RGB_Stars

• Stretch Stars: Stretch RGB_Stars using Generalized Hyperbolic Stretch (GHS) -> RGB_Stars_Stretched

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2. Process Ha & OIII Channels

Next, I work on the Ha and OIII narrowband data:

• DBE: Run Dynamic Background Extraction on Ha and OIII -> Ha_DBE, OIII_DBE

• StarXTerminator: Strip stars from both -> Ha_Starless, OIII_Starless

• NoiseXTerminator: Denoise both -> Ha_Starless_Clean, OIII_Starless_Clean

• Stretch Nebulae: Stretch both narrowband layers using Generalized Hyperbolic Stretch (GHS) -> Ha_Final, OIII_Final

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3. Combine Channels & Add Stars Back

• PixelMath HOO Combine: Combine Ha_Final and OIII_Final in PixelMath -> HOO_Starless

• PixelMath Star Blend: Combine HOO_Starless and RGB_Stars_Stretched -> Final HOO Image

  • For the RGB Stars, you might want to reduce your stars here if they are too bright or big. I use Bill Blanshan’s reduction scripts for this. I don’t remember exactly where I got them so I can’t link to them.

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4. Final Tweaks

• Curves: Run CurvesTransformation on Final HOO Image for final contrast, saturation, and color adjustments.