If you’re into astrophotography, you’ll get to a point where standard tools like Adobe Lightroom and Photoshop will only get you so far. While these tools work as expected from an image editing perspective, astrophotography requires you to work by a slightly different set of rules—often aligning, calibrating, and stacking images of celestial objects—and many standard tools often don’t provide these features.
Enter Siril, a free, open source astronomical imaging software designed to meet the needs of astrophotography enthusiasts. Compatible with Linux, Windows and macOS, it is becoming an increasingly popular choice among amateur astronomers looking for a cost-effective home solution for their imaging needs. We took the 1.2.6 version of the software for a spin to find out how it works.
Siril astrophotography software review
Siril astrophotography software: Prices
- Free due to open source approach
- Frequent updates that are often shared across the community
Specifications
Operating system: Linux (most distros), macOS 10.13 or later, or Windows 10 (64-bit)
CPU: Dual-core processor (Intel or AMD)
WEATHER: 4GB
Storage: SSD is recommended; at least 2 GB free (more for image files)
GPU: Integrated graphics should work (Siril doesn’t require much GPU usage)
Exhibition: 1280 x 768 resolution
Siril is distributed under the GNU General Public License v3.0, which allows users to download, use, and modify the software without charge, as long as proper credit and credentials are given where appropriate. If you use Siril in any of your work, you are asked to credit the software using specific information on the Siril home page. In an age of mass consumer image editing software, this rather DIY, home-spun approach that used to be the norm in the early days of computing is nice to see – and worth supporting.
The software is available for Linux, Windows and macOS, ensuring accessibility for a wide range of users. And because it’s based on community-driven development, the software benefits from contributions from a dedicated group of developers and users who are constantly working to improve its features and performance. The commitment to being a free and open source tool makes Siril an attractive option for budget-conscious astrophotographers, as there are no expensive subscriptions. What you do get, however, is a steeper learning curve and less focus on shiny UI features to help you through the process – there’s a lot to learn in Siril.
Siril Astrophotography Software: User Interface
- Minimal user interface that may be unfamiliar to some
- Easy navigation once you understand the workflow
When you first catch sight of Siril, you’d be forgiven for thinking the overall effect is a bit intimidating, perhaps akin to some of the early image-editing, script-based programs you might have used in years gone by. But it’s worth persevering; Cyril’s interface is organized into tabs that guide users through the sequential steps of image processing, from calibration to enhancement, and it’s pretty well laid out once you know what you’re looking for. Before you delve into anything, visit Cyril tutorial partwhich guides you through everything from getting started with the software to learning how to automate scripts, work with more advanced images, apply noise reduction and complete complex calculations, depending on the results you’re after.
You’ll be presented with an introductory screen, and if you follow the guide, you’ll need to put all the images you want to work with into a separate folder and, within that, four other folders for “darks”, “lights”, “flats” and “distortions”. Once you’ve done that, you can run a preprocessing script that essentially stacks these images for you automatically.
Siril Astrophotography Software: Key Features
- Powerful automated stacking
- Post-processing features that deliver stunning results
Once this stacking is complete, you will be presented with a file to open. This file will render the image with all the combined images together. (It will be placed in your Home folder, and you can open it by pressing Open in the upper-left corner of the Siril window.) You’re not done yet, though. What you will initially be presented with may look like a blurry, black-and-white approximation of what you hope your final image will look like.
There are a few steps to complete, including extracting the background and gradient, and using photometric color calibration to calculate the light emitted by each celestial body to correct the color. This feature is particularly impressive, as the software will connect to global star databases and identify which stars and deep sky objects are in your image. If there is a match, it will automatically adjust the image to correct the color and focus based on those areas of the image you want to highlight. It also offers multiple star alignment methods, including global star alignment and single-star alignment, thus facilitating the accurate stacking of images to enhance the result.
All of this points to an advanced image enhancement feature that sets Siril apart from other image editing software. The feature set includes the essential tools required for high-quality astrophotographic imaging, especially of deeper space and detailed images. The pre-processing features address common issues, such as sensor noise and vignetting, and lay a solid foundation for subsequent processing steps.
Siril Astrophotography Software: Astrophotography Features
- Noise reduction algorithms
- Automated star detection, which is powerful for color correction
In addition to the photometric analysis tools that can enable you to study a variety of dark sky features, the astro capabilities of Siril extend beyond just image processing. Siril can handle a wide range of image and video formats, which provides flexibility in data input and output. It is possible to use the software for a variety of scientific research applications, thanks to the rich detail it provides.
At the heart of Siril is the script model. The ability to create and execute scripts dramatically increases efficiency when dealing with large collections of high-quality images. The best part is that it is also highly customizable. If you know how, you can write your own scripts to edit specific elements of images.
From an astro perspective, one of Siril’s main strengths is the way it handles noise during the stacking process when adjusting and combining multiple exposures. By stacking many frames, Siril uses statistical methods – such as median or mean stacking with rejection algorithms (eg sigma clipping or Winsorized sigma) – to naturally reduce random noise, such as thermal or read noise, while real signals, such as stars and nebulae.
Powerful background extraction and gradient removal tools help suppress unwanted light pollution or uneven lighting that can resemble noise, and post-processing. It offers wavelet-based denoising, allowing users to target noise at different levels of detail. This method preserves fine structures while minimizing grain, which is a critical feature for astrophotography, where the details of your image are everything.
Should you download Siril astrophotography software?
Buy it if:
✅ You want free astrophotography software: Siril is free to use, making it accessible to everyone, but there is a steep learning curve.
✅ You need powerful software: Siril moves beyond the capabilities of Photoshop and Lightroom.
Do not buy it if:
❌ You won’t spend time or effort learning technical, complicated software: Unfortunately, Siril will take his time to navigate and learn to a great extent.
There is a lot to learn in the world of astrophotography, but when it comes to image editing, Siril opens up a whole new world by giving you ultimate control over your images. Because the software is open source, it benefits from a huge amount of online information about it, and there are plenty of tutorials, images to practice on, and expert guidance available for free, which is commendable in itself.
For these reasons, I highly recommend Siril and there are few competitors, especially when you consider that this software is open source and offered to the community for free.
For many people who are happy to tackle the formidable task of learning Siril inside out, there is no doubt that this software will be an invaluable resource for experienced and novice astrophotographers alike. By continuously evolving through community-driven development, Siril ensures that users will always have access to cutting-edge tools to capture and process the wonders of the night sky.
If the Siril astrophotography software is not for you
While Siril has a steep learning curve, Skylum Luminar Neo allows fast editing and is affordable. There are many one-click editing tools available as well as AI tools to make the job easier. If you are looking for a good noise reduction software, DxO PhotoLab 7 should be your favorite. It has the best noise removal tool we’ve tested.
If you just want to edit astro photos, Affinity Photo 2 is the best option. We’ve rated it as the best photo editing app for astro in our best photo editing apps guide. You can stack different types of calibration frames and it has a handy AI editing tool.
