Best Astrophotography Processing Software (2026)

Choosing astrophotography software is harder than it should be. There are a dozen programs, most of them do overlapping things, and the differences that matter are not the ones on the feature lists.

This is a description of what each one is for, what it costs, and which questions actually decide the answer. We make one of them — Akastroid — and you should read the rest of this knowing that.

The three questions that decide it

Everything else is detail.

What do you shoot? Deep sky and planetary are different problems solved by different mathematics. Stacking a nebula means aligning on stars and integrating for hours. Stacking Jupiter means grading thousands of video frames, keeping the lucky few and correcting the atmosphere’s local warp. A tool built for one is rarely the right tool for the other.

How much do you want to decide? Some programs hand you every parameter and expect you to understand each. Others measure the data and choose. Neither is wrong. The first is better when you know exactly what you want; the second is better when you do not yet know what you want, or when you have four targets to get through before work.

What is your time worth against your money? Free tools exist for every job here. They cost learning time instead, and sometimes a great deal of it.

Deep sky

PixInsight — £230 or so, and worth it if you will learn it

The most capable astrophotography software there is. Everything is implemented, correctly, with the mathematics documented — and almost nothing is decided for you.

The learning curve is genuinely steep, and people who say otherwise are usually people who climbed it years ago. Expect to spend months before your PixInsight results beat what you were getting elsewhere. Expect that after those months, nothing else will do what it does.

Best for maximum control, if you enjoy the technical side and will put in the months.

Siril — free, and remarkably good

Open source, actively developed, and the strongest free deep-sky option by a distance. Calibration, registration, stacking, background extraction, photometric colour calibration — all there, all sound.

The interface asks more of you than a commercial tool, and the scripting is where the real power sits. But nothing here is crippled or cut down.

Best for capable deep-sky processing at no cost, if you don’t mind a steeper start.

DeepSkyStacker — free, and does one job

Stacks. Has stacked reliably for twenty years. It does not do the finishing, so you will be leaving with a linear TIFF and taking it somewhere else — usually Photoshop or GIMP.

Best for a dependable stacker, if you already have a finishing workflow elsewhere.

Astro Pixel Processor — around £150, or rental

Strong at the things that are tedious elsewhere: mosaics, multi-session integration, light pollution removal. The interface divides people sharply. Excellent mosaic handling in particular.

Best for mosaics and multi-session integration.

GraXpert — free, and does one thing extremely well

Gradient removal, with a machine-learning model that is better at it than most manual approaches. Not a whole workflow — a single step you drop into one.

Best for gradient removal as a single step in a larger workflow.

Planetary

AutoStakkert — free, and the standard

Grades frames, keeps the sharpest, aligns on multiple points across the disc, stacks. It is the reference implementation of lucky imaging and it is free. Almost every good planetary image you have seen went through it.

It does not sharpen — that is left to a second program, which is why the classic planetary workflow involves three tools rather than one.

Best for frame grading and multi-point stacking, if you are willing to assemble a workflow around it.

RegiStax — free, and the other half

Wavelet sharpening, which is what AutoStakkert leaves out. The two together are the classic planetary workflow: stack in one, sharpen in the other. The wavelet sliders are unintuitive at first and then indispensable.

Best for sharpening a stack produced elsewhere.

PIPP — free, and the preprocessor

Centres the planet, crops, converts formats, sorts frames before stacking. Solves the tedious problems that make a capture awkward to process — problems a modern pipeline should not create in the first place.

Where Akastroid fits

Everything above is a component. PixInsight and Siril process deep sky; AutoStakkert stacks planets and RegiStax sharpens them; PIPP prepares the video first and GraXpert handles gradients. A complete workflow means learning three or four programs and moving files between them.

Akastroid does deep sky and planetary in one place, and decides the parameters from your data instead of asking you for them.

One program, both subjects. Deep sky, planets, the Sun and nightscapes, with the same interface and the same export. No handing a TIFF from one tool to another.

Decided, not configured. Frame grading, calibration, registration, stacking method, gradient removal, colour calibration and the stretch are all measured from your frames. There is no sigma to choose and no stretch to pick — and every decision is written into the log, so you can see what it did and why.

Modern planetary processing. Multi-point alignment that removes the atmosphere’s local warp, per-point frame ranking so each region of the disc takes its own best moments, drizzle reconstruction onto a finer grid, and limb-measured restoration. Wavelet sharpening is built in rather than being a second program.

Nothing leaves your computer. The processing engine contains no networking code at all — not disabled, absent. You can watch the network while it runs.

$49 once, two computers, every 1.x update included. The free tier stacks up to 25 frames a session and keeps working forever.

Which one to choose

You shoot deep sky and want a result tonight — Akastroid. Point it at the folder and read the log afterwards to learn what it did.

You shoot planets — Akastroid, unless you already have the three-program workflow set up and like it. Grading, multi-point stacking, drizzle and wavelets in one pass.

You want to control every parameter yourself — PixInsight, and give it the months it asks for.

You want free and will learn it — Siril for deep sky, AutoStakkert and RegiStax for planets.

Mosaics across many sessions — Astro Pixel Processor, or Akastroid if the panels are already stacked.

What “best” actually means

The best software is the one you will still be using in six months. That usually means the one whose learning curve you can climb, not the one with the longest feature list.

Everything here is free to try, Akastroid included — the free tier is a real tier and not a countdown. Try two or three on your own data rather than the sample sets, and keep the one that gives you an image you like from a process you can stand.