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 0.9.12

What’s new in Siril

This release focused on bug fixes and a better user experience.
Indeed, window management was a bit archaic and a deep refactoring was needed.
Also, histogram window was redesigned to be easier to use.
Recently, source code, roadmap and issues management have moved to Please report issues you encounter with siril on this website, this will help us fix them and make siril a better program.
Remember that Siril is developed without Windows or Mac and that we rely on Windows and Mac users to test and give us feedback about integration or porting problems.


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 bias, 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… 

0.9.12 UPDATE

The 0.9.12 update focused on bug fixes and a better user experience. Indeed, window management was a bit archaic and a deep refactoring was needed. Also, histogram window was redesigned to be easier to use.
Better dialog windows management, Histogram tool refactoring,Provide new strategies for memory management, user can choose in the settings what amount to use, Provide new photometric catalog for color calibration.


New split CFA feature, Script status (line currenty executed) is displayed in a statusbar,TIFF export is now available for sequences, Added new filter: Contrast Limited Adaptive Histogram Equalization (often referred to as CLAHE), Ability to open a sequence by double-clicking on seq file in file explorers.


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, German, 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.

An animation of comet Neowise created by a Siril’s user

Comet NeoWise in the evening sky – above Brünstelkreuz mountain (1734m) The author: Frank Stefani is a beginner in astrophotography (since 6 months),and also been a professional photographer and experienced[…]

Read more

Python to generate Siril script for cooled OSC

A big thank you to Cecile for sharing, maybe it will give you some ideas, so follow this link: Clear skies, Laurent

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