Astro image processing demo : A beginner-friendly workflow with Siril, GraXpert & Affinity.
Quick summary· AI-generated
This beginner-friendly guide walks through processing a real dataset — the Elephant's Trunk Nebula captured with a Vespera 2 over 21 hours in mosaic mode — using free and paid tools. The workflow covers opening linear 16-bit TIFFs in Siril, background cleaning and color calibration, background refinement and noise reduction in GraXpert, star separation via StarXTerminator, and final stretching and color polish in Affinity Photo. The guide includes video and chapter navigation to help users follow along at their own pace, emphasizing that basic familiarity with layer-based editing is sufficient to learn.
Excerpt from Vaonis - Our travel journal
Following our Astro Image Collection Challenge held in November, here's our image processing demo. The image we’re going to build comes from a dataset kindly provided by Vaonis community member Frédéric Courteix. He captured the Elephant’s Trunk Nebula (IC 1396) with a Vespera 2 smart telescope over several nights, then exported a pre-stacked 16-bit TIFF from the Singularity.
In this guide, we’ll walk through a complete processing workflow based on that dataset:
Siril – clean the background and calibrate colors
GraXpert – refine background and reduce noise
Affinity – stretching, color, contrast, and final polish
StarXTerminator (plugin) – separate stars from the nebula
The explanations are aimed at beginners and intermediate users. You don’t need to be an expert to follow along; just some basic familiarity with opening files and working with layers is enough.
Here's the video and transcript.
Quick navigation
Jump to a chapter
1Dataset & tools 2First contact in Siril 3Background in Siril 4Astrometry & colors 5Export linear FITS 6Stretch & star separation 7Curves on the nebula 8GraXpert background & noise 9Final polish in Affinity 10The background isn’t black 11Export & recap
1. The Dataset & the Tools
The data:
Object: Elephant’s Trunk Nebula (IC 1396)
Telescope: Vaonis Vespera smart telescope
Integration: ~21 hours over 8 nights
Mode: Mosaic to frame the whole nebula
Environment: Suburban sky, sometimes with the Moon up
File: Pre-stacked 16-bit TIFF exported from the Vaonis app
Why start from the TIFF and not a JPEG? Because the TIFF is:
Linear (no edit applied yet)
16-bit, preserving faint details and subtle nuances
Much better for serious processing than an 8-bit compressed JPEG
Software we’ll use:
Siril – free, cross-platform astro processing tool
GraXpert – free tool specialized in background extraction and noise reduction
Affinity Photo – paid but affordable; powerful layer-based editor
StarXTerminator – paid plugin for star removal (optional but very useful)
2. First Contact with the Image in Siril
2.1. Open the linear stack
Launch Siril.
Open the 16-bit TIFF from Vespera.
At first it will look almost completely black. That’s normal:
The data is linear, meaning it hasn’t been brightened yet.
All the nebula signal is stuck in the darkest part of the histogram.
2.2. Use the visual stretch (for your eyes only)
At the bottom of the Siril window:
Choose a display transformation (AutoStretch).
Important: this doesn’t…
Comments (0)
No comments yet.