PixInsight 
Linear Image Quality Enhancements

Step 10 (Optional)
Hubble Palette Processing on Color Images from an OSC Camera

updated: 2025-10-26


Purpose

To bring more (false!) color into the image

Activation

Main step: Script > Toolbox > CreateHubblePaletteFromOSC  

Input

any still linear, denoised star-less image from an OSC color camera

Output

a linear color image

Previous Step

Step 5: Noise Reduction

or 

Step 9: Combining the DSO and Stars Image

Next Steps

Improving the Non-LinearImage



General Description


The basic idea how to apply a Hubble palette to a one-shot color (OSC) image in PixInsight is to split the color image according to the wavelengths of the three important frequencies found in typical emission or reflection clouds.

Element

Associated Color

Wavelegth [nm]

SII (Sulfur)

Red

672

Ha (or Hα, H-Alpha)

Green

656

OIII (Oxygen)

Blue

496

This can be done using the scripts available in PixInsight or online. These scripts split the images and, in the case of CreateHubblePaletteFromOSC, recombine the three separate black-and-white images at the end, followed by color adjustments (using e.g. the Curves Transformation process).

  • Pre-processing and Data Acquisition (Implied)
  • Narrowband Filters: 

The ideal scenario for a Hubble palette is using separate H-alpha (Ha) and OIII filters with a monochrome camera, which are then combined into a SHO (or HOO,...) palette. 

  • OSC Data: 

For a single-shot color (OSC) camera, the normalization scripts are designed to extract an approximation of H-alpha and OIII data from your broadband RGB image. 
NOTE: The usage of narrow-band filters, such as the dual-band Optolong L-eXtreme filter, when shooting light frames, may lead to unwanted effects. This filter suppresses all wavelengths except Hα and OIII, blocking the SII wavelength.

Processing steps

  1. Start with the starless image from step 6

Starless Image (identifier: Cloud, postfix: *_Cloud_HT_CT)

  1. Apply a Normalization Script 
    Many scripts are available online that support this wavelength-based normalization. 

Available Scripts:

Script

Where?

CreateHubblePaletteFromOSC

provides different normalization options:
HOO, HSO, HOS, SHO, OSH, OHS, ForaxSHO, ForaxHOO 
and an preview mode

Script > Toolbox > CreateHubblePaletteFromOSC

HOONormalization_V8


Narrowband Normalization – Google Drive
by Bill Blanshan and Mike Cranfield

SHONormalization_V8

HSONormalization_V8

HOSNormalization_V8


Example: Using the HOSNormalization_V8

Script HOSNormalization_V8

Resulting Image
(postfix *_Master_Rotated_GX_BX_NX_SPC_HT_CT_CLOUD_HOS)

/*       Normalize HOS data with Pixelmath - V8

          by Bill Blanshan and Mike Cranfield                */

                    

Mode=           1 ; //<-- Data type, 0: linear, 1: Non-linear

Lightness=      1 ; //<-- 0=OFF, 1=Original, 2=Ha, 3=SII, 4=OIII

SCNR=           1 ; //<-- 0=OFF, 1=On


Blackpoint=  1.00 ; //<-- Blackpoint range (0 to 1= min to med)

SIIBoost=    1.00 ; //<-- Increase to boost SII

OIIIBoost=   1.00 ; //<-- Increase to boost OIII

HLRecover=   1.00 ; //<-- If highlights are clipped, increase >1

HLReduction= 1.00 ; //<-- If highlights are too bright, increase >1

Brightness=  1.00 ; //<-- Increase to stretch image


/* Drag the bottom left arrow over to your HOS image


 Hope you enjoy!!!

.... see next page


  1. Add Stars to Cloud image with PixelMath (save to *_MASTER_BX_NX_GX_HOS_Stars+Cloud)

PixelMath

Resulting De-Linearized (stretched) Image


*_Master_Rotated_GX_BX_NX_SPC_HT_CT_CLOUD_HOS+STARS


Links:

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