A free astronomical image processing software


Siril is targeted to amateur astronomers having acquired images and wanting to process them in a semi-automatic way.


Siril uses modern and powerful processing algorithms running in parallel in order to speed up the time of processing.


Nearly the whole processing chain is available in Siril. With only one software you can produce high quality image for print or web diffusion.

Siril 0.9.10

What’s new in Siril:  New astrometric tool and New comet registration method…

This is the tenth stability release for the 0.9 branch.
It includes fixes for Windows file names handling, many other fixes and a introduces the astrometry plate solving.
With this release, we move away from our subversion code repository and mantisbt bug tracking to use instead. The old services will still be online for a while, but will not be updated.
Please use the new services to report bugs and get the code.


Some highlights of SIRIL

New features are being introduced quite regularly. Here is a list of main features:
Native image format support; Image conversion (to the native FITS format only); Images pre-processing with biases, darks and flats masters; Image registration; Registered sequence export; Image stacking, with optional additive or multiplicative normalization; Enhancement and processing of final images; Image compositing tool, combining and aligning multiple channels; Plotting various pieces of information about an image sequence… 


The 0.9.9 update focuses on the automatisation of the whole pre-processing steps of a complete acquisition by introducing scripts: It allows to siril to be run in console for the first time. Speed of registration has also been improved.


Leveraging the new scripting, Siril 0.9.9 has been integrated as an automatic way of processing acquisitions in the capture software CCDciel. It is now possible to process astronomic images in a total remote way.


So far SIRIL is available for many distributions GNU/Linux, Mac OS, FreeBSD and Windows 64 bits. But as an opensource project its sources can be downloaded, compiled and/or freely modified according to the GPLv3.


English, French, Greek, Spanish, Italian, Dutch (Belgium), Chinese… We are looking for volunteer translators, for the software and for the documentation. No programming experience is required.


Some important keypoints

Siril is fully capable to pre-process and process astronomic images by offering to the users a large set of dedicated algorithms. So far, due to the high level of its star detection algorithm it is quite performant to process deep-sky images in an easy way.


Removing unwanted signal and pattern from RAW images is the main goal of the first step of preprocessing. Siril can of course deal with BIASES/DARKS/FLATS master files.


Siril uses the triangle similarity algorithm coupled to the the RANSAC routine that can deal with a large amount of outliers in the set of input data. Siril can then align difficult cases.


Signal to noise ratio improvement is only possible by cumulating hours and hours of shoot. Siril provides several stacking algorithms that allow to do it in an easy way.


Pre-processing is just the beginning of the astronomical image process. A different set of processing tools is then also available in Siril intended to produce high quality web publication.


Deep-sky lucky imaging processing speed operations.

Thanks to the ability to directly process SER videos, Siril is really adapted to the deep-sky lucky imaging technic. All algorithms work use all cores of the computer, it is then possible to process more than 60 000 frames with no effort.


Unsigned 16-bit FITS files (other FITS are converted to this format on-the-fly)
SER files in its third version
AVI and many other film files. However their support is being dropped in favour of SER.


It is prossible to preprocess SER videos with Darks/Flats/Biases master files. Taking the great advantage of the SER file format, only one more file is created for each preprocess step (Except in one star/planetary alignment where no extra files are created).


Siril sorts best frames using algorithms mainly based upon FWHM. It allows to extract the best set of images that must be used in the final stacking operation.


Each stacking method runs in parallel. In consequence, processing 10 000 images can go as fast than drinking a coffee cup.


For an overview, see some image processing results below.
It’s a highlight of the results obtained with Siril. 

User Testimonials

Don’t take our word for it – here’s what our users say:

I made my first steps with SIRIL Windows … It works perfectly I did some treatments only with SIRIL without other software.
it’s more than very very good
Very powerful Free software. 


So here, I am very conquered by this new version ! … yesterday I finally took the time to test the new version with the scripts proposed … Well it’s just great !….. it is actually even simpler than with DSS !


So that’s cool! I hasten to test this new version as soon as I have something to put on the sensor.

Congratulations for the job, and thank you for this great software.


Install Siril Now! It will only take a minute

Who is behind Siril?

Since April, 2015 the current maintainers are Vincent Hourdin and Cyril Richard, in October, 2016 Laurent Rogé joined the team for documentation and administration of Siril’s Team Moodle.


Maintainer of Siril’s new version

Vincent is a computer scientist (PhD) and uses Siril as an amateur to process images from a Canon EOS, a QSI and a Basler camera on a 410mm telescope.


Maintainer of Siril’s new version

Cyril is a physicist (PhD), now IT engineer at CNRS, motivating new developments and providing high quality processing algorithms to Siril. 



Laurent is a senior IT project manager. He manages the documentation, using Scenari technology and the online training.

Latest News

For latest updates, see our bug and feature tracking system.

Siril 0.9.11 is available

We are glad and proud to announce the release of the new Siril version: 0.9.11. This version containing a lot of improvement is accessible through the download section. For more[…]

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MacOS Bundle

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