Best Software for Astrophotography Processing in 2026: 8 Tools Compared

#1

PixInsight

Best for: Serious deep-sky imagers who want total control

Visit pixinsight.com

PixInsight is the tool experienced imagers measure everything else against. Its modular process system lets you build a chain, calibration, registration, integration, background extraction, color calibration, stretching, sharpening, and save it as a reusable workflow with icons you can drag onto new data. The JavaScript scripting engine and a large plugin ecosystem, including popular paid AI tools from RC Astro, extend it further than any competitor.

That power comes with the famous learning curve. New users routinely spend months before their PixInsight results beat what they got from simpler tools, and the interface makes few concessions to beginners. The license is a one-time purchase that covers all three desktop platforms, and a genuinely full-featured 45-day trial lets you find out whether you are ready for it before paying. Buy it when you can articulate exactly which step of your current workflow is holding you back.

#2

DeepSkyStacker

Best for: First-time stackers who want a result tonight

Visit deepskystacker.free.fr

DeepSkyStacker does one job and has done it well since 2006: take your light frames, darks, flats and bias frames, register them and stack them into a single linear image. The workflow is a short checklist, open files, check all, register, stack, and the defaults are sensible enough that a beginner gets a usable result on the first try. It reads RAW files from most DSLR and mirrorless cameras, which matters because your first deep-sky data will almost certainly come from a camera you already own.

Know its limits. DeepSkyStacker produces a stacked but unstretched linear image, and you will hand that file to another program for the actual processing. It runs on Windows only, and the long-standing homepage now lags behind the GitHub repository where current releases live. None of that matters for its role: it remains the fastest free way to turn a folder of frames into something you can process.

#3

Astro Pixel Processor

Best for: Beginners who want calibration through final image in one app

Visit astropixelprocessor.com

Astro Pixel Processor, usually called APP, is the friendliest route from raw frames to a finished deep-sky image. Calibration, registration, integration, light-pollution removal, star-color calibration and stretching all happen in one guided interface, and the defaults are tuned so beginners get presentable results without understanding every parameter. Its mosaic engine is the standout feature: it models distortion across panels and stitches wide mosaics without pinched stars, a job that is painful in most other tools.

Pricing has two tracks. The renter license costs 60 EUR per year excluding VAT and always includes major upgrades, while the owner license costs 165 EUR once and covers the version you buy plus minor updates. Each license activates on three computers across any operating system. A free 30-day trial covers the whole program. APP is the right buy when Siril feels too technical but PixInsight feels like a second job.

#4

Siril

Best for: Imagers who want a complete free workflow

Visit siril.org

Siril is the strongest argument for never paying for processing software. It calibrates, registers, stacks, extracts backgrounds, calibrates color photometrically, stretches with tools like generalized hyperbolic stretch, and runs deconvolution, all free and open source under the GPL. Scripts automate the repetitive early steps, and recent versions integrate external engines like GraXpert and StarNet++ directly, so the free pipeline keeps getting more capable.

The trade is polish, not power. The interface is functional rather than inviting, and the documentation explains what each tool does more than when to use it, so expect to learn alongside YouTube tutorials. Siril runs on Windows, macOS and Linux, including easy installs through most Linux package managers. For a beginner on a budget, the practical advice is simple: learn the fundamentals in Siril, and only consider paid software when you can name the specific Siril step that limits you.

#5

StarTools

Best for: Imagers who care most about noise and detail fidelity

Visit startools.org

StarTools takes a different philosophical path from PixInsight. Its Tracking engine follows your signal and its noise component through every step, which lets it do things like mathematically correct deconvolution on already-stretched data and noise reduction that seems to know exactly where the grain lives. In practice, imagers who switch to StarTools often report cleaner detail with less effort spent fighting noise.

The interface is the hurdle. It does not look or behave like Photoshop, PixInsight or anything else, and the workflow concepts take deliberate learning. The license is refreshingly simple: 69 AUD once, yours forever, with updates for two years, no subscription and no activation drama. The free trial runs every feature and only blocks saving, so you can process your own data end to end before deciding. It suits the imager who finds PixInsight overkill but wants more sophisticated processing than the free tools offer.

#6

GraXpert

Best for: Anyone fighting gradients and noise, whatever their main tool

Visit graxpert.com

GraXpert started as a better gradient remover and grew into an AI toolkit. Its headline feature is AI background extraction: instead of placing dozens of sample points the way PixInsight's DBE demands, you let the trained model find the background on its own, which handles complex uneven backgrounds remarkably well. Version 3 added AI denoising, and later releases added AI deconvolution models split for stars and deep-sky objects separately.

It works two ways. As a standalone app it processes FITS and TIFF files on its own, and as a module it slots into PixInsight and Siril workflows, which is how most serious imagers use it. Everything is free and open source on GitHub. GraXpert will not replace your stacker or your main processor, but it has become the default answer to the two most annoying steps in deep-sky processing, and the price cannot be argued with.

#7

RegiStax

Best for: Planetary, lunar and solar imaging from video

Visit astronomie.be

Planetary imaging is a different sport from deep-sky work. Instead of long exposures you record thousands of video frames, keep the sharpest few hundred, and stack those. RegiStax was built for exactly this by Dutch amateur Cor Berrevoets, and its align, stack and wavelet sharpening pipeline remains the reference workflow for planets, the Moon and the Sun. The wavelet sliders let you pull fine detail out of a stacked video in a way general-purpose editors cannot match.

It is free, Windows-only, and unapologetically old-school in appearance. Development has been quiet for years, yet nothing free has displaced it for lucky imaging, and many planetary imagers still pair it with AutoStakkert for the initial stacking. If your targets are Jupiter, Saturn or lunar craters rather than nebulae, RegiStax belongs in your toolkit from day one.

#8

Sequator

Best for: Milky Way and nightscape stacking without a star tracker

Visit sites.google.com

Sequator solves the beginner's dilemma: you want a clean Milky Way image but you do not own a star tracker. It aligns the stars across a stack of short exposures, averages out the noise, and composites a separate foreground exposure so the ground stays sharp while the sky stacks clean. Auto-brightness and HDR output modes keep the exposure under control, and it is unusually capable under light-polluted skies.

The interface follows a strict philosophy of few options with automatic parameter detection, so there is almost nothing to configure and little to get wrong. It reads RAW files and exports 16-bit TIFFs for further editing in Photoshop or GIMP. Sequator is not a deep-sky calibration tool and will not replace DeepSkyStacker for telescope work, but for tripod nightscapes it is the fastest free path from a memory card to a clean stacked image.