AkastroidComparison
Akastroid vs DeepSkyStacker
DeepSkyStacker is free, it is Windows-only, and it has stacked more amateur astrophotographs than any other program alive. The difference is not the stack. It is everything on either side of it.
The short answer
Stay with DeepSkyStacker if you are on Windows, you already finish your stacks in Photoshop or GIMP and enjoy that part, and your mount tracks well enough that frame rejection is not a problem you have.
Try Akastroid if you are on a Mac, if you shoot on an alt-az mount or a smart telescope, if the step you get stuck on is the one after stacking, or if you also image planets and would rather not run four more programs to do it.
Where DeepSkyStacker is genuinely better
It is free, permanently and without a frame limit. That is not a small thing and it is the first thing anybody comparing the two should weigh. It has been in use for two decades, which means every problem you might hit has been hit and written up by somebody already - the volume of community answers around it is a real advantage that no newer program has.
It also gives you complete manual control of which frames go in and how they are combined, with no opinion of its own. If you have already learnt what those settings do, being asked for them is a feature rather than an obstacle.
Where the two actually differ
| DeepSkyStacker | Akastroid | |
|---|---|---|
| Cost | Free | Free to 25 frames a session, then one payment |
| Platforms | Windows | macOS now, Windows in test |
| Deep sky stacking | yes | yes |
| Darks, flats and bias | yes, loaded per set | yes, found in darks/ and flats/ |
| Camera RAW read directly | yes | yes |
| Field rotation (alt-az mounts) | limited | star-pattern registration |
| Named reason for each rejected frame | no | yes, twelve measurements |
| Light pollution gradient removal | no | yes |
| Photometric colour calibration | no | yes, against a star catalogue |
| Stretching, denoise, sharpening | no | yes, measured from the data |
| Planetary and lunar video | no | yes |
| Runs entirely offline | yes | yes |
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 a comparison that claims a dramatic difference in integration quality between two competent stackers is overselling.
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 colours are. How far to stretch before the background goes grey. Those are the steps where an image is won or lost, and they are the steps DeepSkyStacker leaves to you and to 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 - and it shows up as stars streaking into arcs towards 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 describes your night - the hour the transparency dropped, the moment the dew arrived - rather than issuing a verdict. 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 colour calibration against half a million catalogued 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 - the job normally split across PIPP, AutoStakkert and RegiStax.
What Akastroid does not do
Its adjustments are global. There are no masks, no layers and no 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 - though it still works well as the front half, because the integration can be saved before any finishing is applied and taken elsewhere.
The free tier is capped at 25 frames a session. That is enough for a real image from a real night and it is not enough for a five-hour integration, which is the honest shape of the trade against something that is free without limit.
Try it on the same data
The only comparison worth anything is the one run 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.
Questions
Is DeepSkyStacker available for Mac?
No. DeepSkyStacker is a Windows application, and Mac users generally reach it through a compatibility layer or a virtual machine, or use something else. Akastroid is built natively for macOS, with a Windows build in test.
Does Akastroid stack better than DeepSkyStacker?
For a well-tracked session on an equatorial mount, the integrations are comparable and you should not expect a transformation - stacking is well-understood mathematics and both do it correctly. The differences show up in three specific places: frames that rotated because the mount was alt-az, sessions where some frames are ruined and need to be identified, and everything that happens after the stack.
What does Akastroid do that DeepSkyStacker does not?
The processing after the stack. Gradient removal, photometric colour calibration against a star catalogue, stretching set from the image's own histogram, deconvolution with a measured point spread function, and denoising. DeepSkyStacker's job ends at the integration and expects you to finish it in Photoshop or elsewhere. Akastroid also handles planetary and lunar video, which DeepSkyStacker does not do at all.
DeepSkyStacker is free. Why pay?
If DeepSkyStacker is producing images you are happy with, keep using it - that is a genuine answer and not a polite one. The case for paying is the finishing workflow you would otherwise assemble from other tools, native Mac support, frame diagnostics that name the fault, and planetary work in the same application. Akastroid is free for sessions up to 25 frames, so the comparison can be made on your own data before any money changes hands.
Can I use both?
They are both stackers, so there is little point running one after the other - pick one for the stack. What does combine well is using Akastroid for the stack and something else for the finish: Save the stacked image, unprocessed writes the integration before any stretching, colour or sharpening is applied, which is exactly what Photoshop, GIMP or PixInsight want as a starting point.
Run them side by side
Free for sessions up to 25 frames. No account, and nothing leaves your computer.