What Akastroid Replaces, and What It Doesn't

Every piece of astrophotography software claims to replace the others. Most of those claims fall apart once you have a specific requirement, because the tools really do different things.

This is where Akastroid stands, including the cases where you should use something else.

Our recommendation

For most people the answer is Akastroid: one app for deep sky, planets, the Moon and the Sun, on Mac, Windows and Linux. You drop in your frames and it grades, calibrates, stacks, removes the gradient, calibrates the colour and sharpens, with no settings to choose. The usual route needs four to six separate programs for the same result.

On the same Orion stack, Akastroid’s automatic finish measured a signal-to-noise of 402 against 87 for Siril’s standard workflow, with a sky gradient of 2.6% against 21.6% (the full comparison). It is free to try on your own data.

Choose PixInsight if you want to control every step by hand and will spend months learning it, or Siril if you want free software and are happy to learn the steps. The rest of this guide compares them in detail.

The stack most people end up running

A typical planetary workflow is four applications: PIPP to center and crop the capture, AutoStakkert to grade and stack, RegiStax or WaveSharp for wavelet sharpening, and WinJUPOS if you want to de-rotate across a long capture. Each writes an intermediate file the next one reads. (A step-by-step map of that chain onto one window.)

A typical deep-sky workflow is Siril or Deep Sky Stacker to calibrate and stack, then PixInsight or Photoshop to finish, and more and more often a paid add-on like BlurXTerminator or StarNet.

Nothing is wrong with either. Both grew out of people solving real problems well. They do carry two costs that are rarely stated plainly.

The first cost is learning time

I mean the time it takes to learn the tools, not the processing time itself.

PixInsight is the deepest astrophotography tool available and close to a career in its own right. The interface predates modern conventions, the documentation assumes signal processing vocabulary, and the general view in the community is that it takes months to become competent. That is a fair trade for what it gives back, but it is a real cost and it stops a lot of people.

The four-application planetary chain has a subtler version of the same problem. Each tool on its own is approachable. The sequence is where people get lost: which order, which intermediate format, what settings in PIPP so AutoStakkert behaves, why the result is soft when every individual step looked fine.

Akastroid’s approach is that most of those decisions depend on the data rather than on preference, so they can be measured instead of asked.

Which stacking method suits your data depends on how many frames you have and how much the sky drifted, and both are measurable. How hard to deconvolve depends on your measured star width and signal-to-noise. Whether drizzle helps depends on whether your frames were dithered, which is in the frames. Where to set the black point depends on what fraction of the frame is sky. On a wide field that is around 98%, and the right target is roughly a third of the generic default.

None of those are matters of taste. They are measurements people currently make by eye, after months of learning to.

The second cost is money, and it is more than the licences

PixInsight is around €300 for a one-time licence carrying a year of updates. BlurXTerminator is around $100. StarNet is free, but StarXTerminator is around $80. A working PixInsight setup with the popular add-ons is comfortably over €400 in the first year.

Siril is free and very good. If budget is the constraint and you are willing to learn, Siril plus its scripts will get you a long way at zero cost.

Akastroid is $79 (launch price until 31 October) once for one computer, $149 for two, with a free tier and a 14-day refund. That is the licence comparison, and it is only part of the picture.

The larger saving is clear nights not wasted. The scarce thing in astrophotography is transparent, moonless, cloud-free time. Finding out in March that your January data was unusable because of something in the capture (dew on the second half, a focus shift you did not catch, dithering you thought was on) costs you the session, not the processing hour. If grading at import tells you what was wrong with which frames, you can plan the next clear night instead of repeating the last one.

What each level of experience gets out of it

Beginners get a real result on the first attempt, and can learn from it. Session details lists every decision with its reason, so you can see what a reasonable workflow did and why.

Intermediate imagers get the corrections they know they should be doing and often skip. Photometric color calibration against a star catalog is standard practice among experienced imagers and rare among everyone else, mostly because setting it up is fiddly. Here it is on by default when your frames record where they were pointing.

Experienced imagers get triage. A hundred-frame session takes a few minutes and produces a finished image, which is enough to know whether the data is worth two hours in PixInsight. The “Save the stacked image, unprocessed” export writes the integration before any finishing, so Akastroid can be the front half of a workflow that ends somewhere else. Calibrate, register, reject and integrate here, then finish in the tools you already know.

Where the other tools are still better

Masks and selective editing. Akastroid’s adjustments are global. PixInsight’s range masks, luminance masks and PixelMath, and Photoshop’s layers and luminosity masks, let you apply a correction to part of an image. That is the largest capability gap, and it is what separates a processed image from a finished one at competition level. If your workflow depends on masks, Akastroid is not a replacement.

Planetary de-rotation. WinJUPOS compensates for Jupiter’s rotation so you can stack across ten minutes instead of two or three. That multiplies your usable frames far beyond what better stacking alone recovers. Akastroid has no equivalent. For serious Jupiter work you still need WinJUPOS.

Per-alignment-point frame ranking at scale. AutoStakkert’s reputation rests on ranking every frame at every alignment point independently, so a frame sharp on one limb and soft on the other contributes only where it is good. Akastroid does this too, and measured on a 114-frame capture it was worth about 1%, because the technique needs thousands of frames before local seeing variation gives it enough to choose from. On a long, deep planetary capture, AutoStakkert is still ahead.

Deconvolution. BlurXTerminator is better than what Akastroid does, which is regularised Richardson-Lucy with a PSF measured from the frame’s own stars. Akastroid’s version is automatic, declines when it would do harm, and is included. It is not state of the art.

Scripting and batch depth. Siril has a scripting language and a CLI. If you process on a schedule or in volume with custom logic, that is a real advantage.

Recommendations

• New to this, on a smart telescope or a DSLR: Akastroid. The learning curve is what stands between you and a photograph, and removing it matters more to you right now than any individual algorithm.
• On a budget and willing to learn: Siril. It is free and it is good.
• Committed, chasing the best possible image, with time to invest: PixInsight. Nothing else has its depth, and the masking model alone justifies it.
• Serious about planets: keep AutoStakkert and WinJUPOS. Akastroid matches them for convenience, not for ceiling.
• Experienced, with more data than processing time: Akastroid for triage and integration, your existing tools for finishing. The free tier lets you test that combination at no cost.

What it does, stated precisely

Akastroid does not beat four specialized applications at what each does best. It gets you most of the way there in one application, in a few minutes, without a learning curve, and it tells you what it decided and why. It also applies corrections that experienced imagers make routinely and most others skip.

For many people that is the difference between having finished pictures and having folders of unprocessed FITS. For others it is a fast front end to a workflow that finishes elsewhere.

If you need masks and de-rotation, keep the tools that give you those.