Akastroid vs DeepSkyStacker

The short answer

Choose Akastroid if you want a finished picture, not only a stack. It removes the light pollution gradient, calibrates the colour against a star catalogue, stretches, denoises and sharpens on its own, and tells you why each rejected frame was rejected. It runs on Mac, Windows and Linux, where DeepSkyStacker is Windows only (the usual Mac workarounds are Wine or a virtual machine). It handles alt-az mounts and smart telescopes, and it does planets and the Moon in the same app.

DeepSkyStacker suits you if you are on Windows, you only want a free stacker, and you enjoy finishing every stack by hand in Photoshop or GIMP.

Where the two differ

The stack is not the hard part any more

Stacking is settled mathematics. Align the frames, reject the outliers, average what remains, and the noise falls with the square root of how many frames you had. Every serious program does this correctly, and I would not trust a comparison that claims a big difference in integration quality between two competent stackers.

What is not settled is everything around it. Which of your frames were ruined and by what. Whether the field rotated. Where the sky gradient is and how to remove it without taking the nebula with it. What the real colors are. How far to stretch before the background goes gray. Those steps decide how the picture turns out, and DeepSkyStacker leaves them to you and whatever you open the result in.

Field rotation

Akastroid registers by matching star patterns rather than searching for a shift, so a field that rotated between exposures still aligns. This is the case that decides whether an alt-az session stacks at all (a Seestar, a Dobsonian, an undriven mount). When it goes wrong it shows up as stars streaking into arcs toward the frame corners when it goes wrong.

Rejections that say what was wrong

Twelve measurements are taken on every frame: star size and shape, star count, drift, background level, gradient strength, noise, signal-to-noise, cloud, satellite and aircraft trails, focus and clipping. Each rejected frame names the fault, so the frame table shows the hour the transparency dropped or the dew arrived, not just a pass or fail. Any rejection can be overruled with a click. See Image Doctor for what each measurement means.

The half of the workflow that comes after

Gradient removal, photometric color calibration against 1.48 million cataloged stars, a stretch set from your own histogram, deconvolution with a point spread function measured from your own frame, and denoising scaled to the stack's measured noise. In a DeepSkyStacker workflow all of that happens in another program, by hand. The full workflow is written out here.

Planets and the Moon

DeepSkyStacker does deep sky. Akastroid also reads SER and AVI captures, grades every frame for sharpness, aligns in pieces to remove the atmosphere's local warping, corrects atmospheric dispersion and sharpens with wavelet layers. That job is normally split across PIPP, AutoStakkert and RegiStax.

What DeepSkyStacker does well

It is free, without a frame limit, and it has been in use for two decades, so there is a lot of forum help around it.

It also leaves every stacking setting to you. If you already know what those settings do, that control is useful. If you would rather not learn them, Akastroid measures your frames and chooses for you, and every control is still there when you want it.

What Akastroid does not do

Its adjustments are global: it has no masks, layers or selective editing, so a correction applied to the core is applied to the background too. If your workflow depends on luminance masks, this is not the tool for the finishing pass. It still works as the front half, because the integration can be saved before any finishing and taken elsewhere.

The free tier is capped at five processing runs and two exports, not by feature or frame count. Every session stacks in full, twenty frames or five hours of them. After that it is a one-time payment for every future version.

Try it on the same data

The comparison that matters is on your own frames. Point both at the same folder and look at the two results. The wider comparison, including Siril, PixInsight and AutoStakkert covers the rest of the field.