Tool profile
Siril: cost, fit and limits
Siril is an open source astronomical image processing program developed by the Siril project that aligns, stacks, calibrates and stretches astrophotos, with scripts for automatic processing and optional manual control of each step. It is aimed at amateur imagers and scientific users.
What to know first
Siril processes images after capture. The homepage and about page describe automatic or manual alignment and stacking of image sequences including SER films, outlier rejection, color calibration, deconvolution and histogram stretch, plus astrometry that gives information about the objects in an image. The pages read show no price and name no AI. The shop sells a manual and merchandise, and scientific use asks for a citation of a Journal of Open Source Software paper.
Siril at a glance
| Maker | Siril project, Not stated on the vendor pages |
|---|---|
| Free plan | No |
| Entry price | Quote only |
| API access | No |
| Category | Best AI Astronomy Software in 2026, rank 7 of 13 |
| Website | siril.org |
Who Siril is best for
Imagers finishing a night's frames
Alignment, stacking and outlier rejection turn a set of registered images into one cleaner result, which is the step after capture in any workflow.
Users who like scripted processing
Scripts handle automatic processing, while manual control of each step stays available when you want to inspect a result. The two modes mean beginners can follow defaults while experienced users inspect each result.
Scientific users
The about page asks for a citation of the Journal of Open Source Software paper when Siril is used in scientific work.
Siril plans and pricing
| Plan | Price | What it includes |
|---|---|---|
| Siril (open source) | Not published on the pages read | Downloads and source code from the Siril site. A manual by the principal developer is sold separately in the shop. |
Checked November 2026.
What Siril does
- Alignment and stacking
- Image sequences, including SER films, can be aligned and stacked automatically or by hand. Sequences are the sets of frames from a night, and SER films are the format planetary imagers often use.
- Outlier rejection
- Rejection routines reduce noise when many registered images are stacked, according to the homepage. Rejection routines are part of what makes a stack cleaner than any single frame.
- Color and detail steps
- Color calibration, deconvolution and histogram stretch are listed as steps before publication of the final image. These steps come before the finished image is published, and each can be adjusted by hand.
- Astrometry interaction
- Interaction with astrometry gives information about the objects found in an image. This links the stacked image to catalog data about what it shows, which helps identify objects.
- Scripting
- Scripts run an automatic processing chain, or you control each step yourself, depending on how much you trust the defaults. The scripts save repeated clicks when you process many nights the same way.
How Siril handles your data
The Siril privacy policy says comments on the site keep an IP address and browser user agent for spam detection. It does not otherwise state a retention period, hosting region or certification, and nothing on the pages read says customer data trains AI models. The program works on image files on your own computer, so the processing itself does not need an account. The shop sells a manual and merchandise, so order data handling there falls under the shop's own terms, which were not read.
Where Siril falls short in practice
- Manual languages. The official manual is available in English, French and Italian. German and Spanish are announced as coming soon on the shop page. The English manual is the one to rely on for now.
- Paid manual. The principal developer's manual is sold separately, so thorough documentation can cost money even though the pages read show no price for the program. That is a small expectation, but it applies to anyone publishing results.
- Processing only. Siril is described as image processing only. You still need a separate planetarium and capture program for the rest of the workflow. Documentation has a cost even though the program shows no price.
Alternatives to Siril
Siril: common questions
What does Siril do?
Siril processes astronomical images. It aligns and stacks sequences, including SER films, rejects outliers, calibrates color, deconvolves and stretches the histogram, and it can run scripts. The pages read describe no image capture or telescope control. Capture and charting are done in other programs.
Is Siril free?
The pages we read show Siril as an open source project with a Source Code link and downloads, and show no price for the program. The shop sells a manual and merchandise. Confirm current terms on the official download page before relying on that.
Does Siril use AI?
The pages we read name no AI feature for Siril. Its steps are described as alignment, stacking, outlier rejection, calibration, deconvolution and stretch, which are classic processing methods. If AI is a requirement, check the project's documentation for newer additions.
Is there a Siril manual?
Yes. The shop page sells the principal developer's manual, available in English, French and Italian, with German and Spanish announced as coming soon. Online documentation and the website pages may also help, but they were not part of this review.
How should I cite Siril in research?
The about page asks scientific users to cite the Journal of Open Source Software paper. If your work depends on Siril's stacking or calibration results, cite it in the references and state the version, so that others can repeat the processing.