New PixInsight process: Narrowband Normalisation

A new process for PixInsight has been released: NarrowbandNormalization. This process is used to balance the individual colour channels in narrowband images. The input is a (preferably starless) RGB image with narrowband channels mapped to a colour palette. It works for both OSC and monochrome cameras.

When combining narrowband images in for example a Hubble palette, the initial result is often disappointing. The brightness between channels can be very different and often needs adjusting. In broadband images the color calibration process takes care of this. But for narrowband images, this is more difficult. There are difficult ways to do it, but it always involves multiple steps, and there’s no direct feedback on what the end result will look like.

With this new tool that all changes. You tell it the palette of the image (e.g. HOO, SHO, etc). Then you turn on the real-time preview and you the normalised image shows up. This might even be enough. But it does not stop here. There are lots of tools to fine-tune the final result. Different (adjustable) blendmodes for the green channel in an OSC image. Different options to handle the lightness channel. Individual adjustment of OIII and SII channel in monochrome image. Built-in SCNR to control the amount of green. Additional options to adjust shadows, highlights and brightness.

The process is developed by Bill Blanshan and Mike Cranfield. It is an evolution of Pixelmath scripts originally developed by Bill. Mike has enhanced the math behind it and developed it to a process. The tool is available free of charge. To install it in PixInsight, follow these steps:

• Go to Resources > Updates > Manage repositories. Select ‘Add’ and copy the following repository address into the url field:
  https://www.cosmicphotons.com/pi-modules/narrowbandnormalization/

• Click OK.

• Go to Resources > Updates > Check for Updates

• The system will find the new tool (and maybe more updates). Select Install

• Close PixInsight. The updater will pop up and ask to install the updates. Select Yes.

• Restart PixInsight and the tool can be found under Process > ColorCalibration > NarrowbandNormalization

The tool comes with extensive documentation built in. In addition, Bill has released a video on YouTube with detailed explanation on how to use it. Note that the tool only works with PixInsight version 1.8.9-2, so make sure you have upgraded PixInsight to this recent release.