Experimenting with the new PixInsight Tool - VeraLux HMS

Like in any tech field, advancements in technology, tools, and processes keep pushing the boundaries of what’s possible, and astrophotography is no exception. Just last week, a new tool called VeraLux HyperMetric Stretch, originally created for Siril/Python by Riccardo Paterniti, was released as a script for PixInsight, my preferred processing software. Touted as the “next best thing since sliced bread” and a “game changer” for astrophotographers, I couldn’t resist giving it a try to see what all the buzz was about.

Although I first tried it on my latest photo of the M35 star cluster (shown below), I was eager to really put it to the test on a narrowband image.

I chose IC1848, the Soul Nebula, for its expansive nebulosity and rich stellar gas. I first photographed it in November 2022 and added more data in December 2023. The original 2022 image was over-processed, with excessive vibrancy. After adding the new subs in 2023, I re-processed the image using some new software tools that weren’t available back in 2022—Russell Croman’s BlurXterminator and NoiseXterminator - and with new wisdom of how to properly handle image stretching and color enhancement.

November 2022

December 2023

The difference is clear. The 2022 image was a bit over-the-top, with overly saturated colors and contrast so strong it hid some details in the heart of the nebula. The 2023 image, on the other hand, offers a more subdued and realistic look, revealing intricate details throughout the inner nebula. While the additional data from 2023 played a big role in enhancing the detail, the processing was also done with a softer, more refined touch.

December 2025 - enter VeraLux HyperMetric Stretch. VeraLux operates on a fundamental axiom: standard histogram transformations often destroy the photometric relationships between color channels (hue shifts). And although one can (and I have) spend hours using the existing stretching tools to accomplish the same task Veralux does it with a single push of a button (well, maybe two). Here is the result of taking the original calibrated subs from the 2023 version of the nebula and using Veralux as the only stretching process.

The results are impressive. With minimal effort, I matched the outcome without the tedious manual stretching required by HistogramTransformation (HT) or GeneralizedHyperbolicStretch (GHS). The stars look less bloated and more vibrant, and the subdued star field really makes the nebula stand out as the focal point of the image. I do wonder about the authenticity of some of the star colors, but overall, the result is solid.

VeraLux is still in its beta stage, and I expect it to keep improving, but it has already secured a spot in my toolbox as my go-to stretching software.