Our verdict: Siril takes astrophotos from raw frames to a finished image in one free program. Ready-made scripts make the standard calibration and stacking workflow almost automatic, and manual tools give full control later. The interface and terminology assume you know the basics of astro processing.
About Siril
Siril is developed by the Free-Astro team under the GNU GPL v3. It handles the whole pre-processing chain: calibration with bias, dark and flat frames, registration and stacking with outlier rejection, all using every CPU core.
After stacking, it offers post-processing such as background extraction, color calibration, deconvolution and histogram stretching. It also has scientific tools for photometry and astrometry. Thanks to native SER and FITS support, it can process tens of thousands of frames from lucky imaging videos.
What it does well
- Calibration. Builds master bias, dark and flat frames and applies them to light frames.
- Registration and stacking. Aligns frames on stars or planetary surfaces and stacks them with outlier rejection.
- Scripts. Ready-made scripts run the standard workflow automatically, and you can write your own.
- Post-processing. Background extraction, color calibration, deconvolution and histogram stretching.
- Science tools. Photometry for variable stars and exoplanet transits, plus plate solving.
Who it is for
Good fit
Amateur astrophotographers with DSLR, mirrorless or dedicated astro cameras who want a free stacking and processing tool.
Look elsewhere
Beginners who want one-click results without learning about calibration frames and stretching.
Pros and cons
Pros
- Free and open source
- Complete workflow from raw frames to final image
- Fast multi-core stacking
- Scriptable and well documented
Cons
- Steep learning curve for newcomers
- Some post-processing still easier in other tools
How to install Siril
Download the Windows installer from the official download page; the file is served from free-astro.org, the project's own server. A portable ZIP is also offered. Use the latest stable version, not the beta or RC builds listed under previous versions.
Questions about Siril
Is Siril free?
Yes. Siril is open source under the GNU GPL v3 and completely free, with no paid edition.
Can Siril stack DSLR RAW files?
Yes. Siril reads camera RAW files as well as FITS, TIFF and SER videos, and can stack them.
Siril or DeepSkyStacker?
DeepSkyStacker focuses on stacking with a simple workflow. Siril also covers post-processing, scripting and scientific analysis.
