Siril
Technical sheet for Siril, the free and open source astronomical image processing software (stacking, calibration, astrometry).
Description
Siril is a free and open source (GPL v3) astronomical image processing software, developed by the free-astro association. It covers the whole post-processing chain: raw file conversion, pre-processing (calibration with bias/dark/flat frames), registration and stacking of images, up to finishing steps (wavelets, histogram stretching, noise reduction…).
Available on Windows, macOS and Linux, it’s scriptable for automating repetitive tasks, and includes built-in astrometry (plate solving) as well as photometry tools (light curves, variable star tracking, exoplanet transits).
Technical specifications
| Specification | Value |
|---|---|
| Type | Astronomical image processing software |
| Publisher | free-astro (community project) |
| License | Free/libre, GNU GPL v3 |
| Platforms | Windows, macOS, Linux |
| Core features | Conversion, calibration (bias/dark/flat), registration, stacking, wavelets, histogram stretching |
| Astrometry | Built-in plate solving |
| Photometry | Light curves, variable stars, exoplanet transits |
| Automation | Dedicated scripting language, command-line processing |
| Supported formats | FITS, SER, TIFF, camera RAW formats, PNG/JPEG |
Values from official specifications, to be refined with real-world use.
Official site: Siril
Strengths
- Completely free and open source, with no feature limitations.
- Covers the whole post-processing chain, from raw subs to the final image.
- Scriptable: great for automating stacking across a large batch of sessions.
- A good entry point before eventually moving to a more advanced tool like PixInsight.
Coming up
This sheet will be expanded with feedback on the stacking workflow used, custom scripts, and a practical comparison with PixInsight.