PIPP, AutoStakkert and RegiStax in One Window

If you have processed a planet before, you know the sequence. Open the capture in PIPP to centre and crop it and write a new SER. Open that in AutoStakkert to grade the frames, set alignment points, stack the best fraction and write a TIFF. Open the TIFF in RegiStax and pull the wavelet sliders until the belts appear. Three applications, two intermediate files, and a set of settings in each that you learned once and now copy from a forum post.

None of the three is bad software. Together they are the reason planetary imaging feels like a craft with an apprenticeship. This post walks the chain step by step and shows where each step lives in Akastroid - and, because a comparison without the losses is an advertisement, what the originals still do that this does not.

Step one: PIPP - centre, crop, discard

PIPP’s job is preparation. It finds the planet in every frame, moves it to the centre, crops the frame down to a box around it so the stacker is not aligning on empty sky, throws out frames where the planet clipped the edge or the exposure jumped, and writes a clean SER for the next tool.

In Akastroid this is the first thing that happens when a capture is opened, and there is no file at the end of it. Every frame is located - the disc’s centroid, measured to a fraction of a pixel - and its brightness inside the disc is recorded alongside its sharpness, so a passing cloud or a gain change shows up as a brightness dip and the frame is ranked accordingly. Frames where the planet ran off the sensor are simply not usable and are marked so. The crop to the planet is a button on the result, and it is optional because some people want the moons in the frame.

What you lose: PIPP’s output options. It can write an AVI for a different program, split a long capture into chunks, or produce a centred animation. If PIPP was a hub in your workflow rather than a step in it, that hub is not here.

Step two: AutoStakkert - grade, align, stack

This is the step that makes the image. AutoStakkert measures how sharp every frame is, sorts them, lets you choose what fraction to keep, places alignment points across the disc, and then stacks each point’s patch from the frames that were sharpest there rather than sharpest overall. That last idea - local quality ranking - is why it displaced everything before it.

Akastroid does the same three things, with two differences worth knowing about.

Grading measures each frame’s fine-scale structure relative to its own noise rather than raw edge energy, because raw edge energy rewards noise: a noisy frame has plenty of high-frequency content and none of it is Jupiter. The ranking is shown as a frame browser you can scrub through from best to worst, which is the fastest way to see what the atmosphere did to your evening.

The keep fraction is read off the capture, not typed in. The conventional “best 25%” is right for some captures and wrong for others, and which one you have is in the data. On a Jupiter capture in steady air the top quarter of frames all scored 75 or better against the best frame’s 100; stacks at 25%, 12% and 6% were indistinguishable. On a Saturn capture in rough air the top quarter reached down to 48, with the median frame at 40, and 12% gave measurably sharper belts than 25% for a small cost in noise. Akastroid keeps the frames that are within a quarter of the best, capped at the conventional quarter of the capture, and shows you the number so you can override it. (More on how that was measured.)

Alignment points are placed automatically on the parts of the disc that have structure to align on - a limb, a belt edge - and each point ranks the frames locally. Where AutoStakkert keeps a fixed fraction at each point, Akastroid weights continuously: a frame that was sharp at a point contributes fully there, a frame that was soft contributes in proportion, and there is no cliff where frame 499 counts and frame 500 does not.

What you lose: manual alignment-point placement, and scale. AutoStakkert lets you put points exactly where you want them, and on a very long capture - ten thousand frames of a large, detailed disc - its local ranking has more to choose from than Akastroid’s does. Measured on a modest capture the difference is a percent or so; on a long, deep one AutoStakkert is still the reference.

Step three: RegiStax - wavelets

RegiStax’s wavelet sharpening is the reason the technique produces images that look the way they do. The stack is decomposed into layers by spatial scale, each layer is amplified by a slider, and the image is rebuilt. Detail at the scale of a belt gets lifted; noise at the scale of a pixel does not have to be.

Akastroid’s sharpening panel is the same tool with the same six scales, from Finest to Coarsest, each with its own noise suppression. The starting values are not a preset: they are tuned from the stack - a deep stack in good seeing gets its finest layer lifted because at that depth the finest scale holds detail rather than noise, a thin or soft stack does not. The sliders re-render instantly and the stack is not redone.

Two things RegiStax users reach for are also here. RGB align measures the offset between the colour channels and corrects atmospheric dispersion - the red-on-one-limb, blue-on-the-other fringe a low planet always has - to a fraction of a pixel. Restoration is a deconvolution with the blur measured from the planet’s own limb; it is off by default because deconvolution invents plausible detail with the same confidence it recovers real detail, and a planet has no star in the frame to check the answer against. Raise it slowly and compare.

What you lose: RegiStax’s linked wavelets, its histogram and RGB balance tools, and its per-layer preview. If you have a RegiStax recipe you trust for a particular target, the sliders here will get you close but they are not a port of that recipe.

What none of this replaces

WinJUPOS de-rotation. Jupiter rotates fast enough that a capture longer than about ninety seconds smears its own surface. WinJUPOS compensates, so you can stack across ten minutes instead of two. Akastroid has nothing equivalent, and for serious Jupiter work it remains the tool. It is free.

Batch depth. AutoStakkert will chew through a folder of fifty captures overnight with one settings file. Akastroid has a batch mode for deep-sky sessions; planetary captures are processed one at a time.

The honest summary

The three-application chain exists because each step was solved separately, by different people, at different times. There is no technical reason for the seams between them; the intermediate files are history, not design. Akastroid removes the seams and makes the decisions that were always determined by the data - the keep fraction, the alignment points, the starting wavelet values - from the data.

If you are learning, that is most of the apprenticeship gone. If you already have a workflow that produces images you are proud of, the reasons to switch are convenience and the frame browser, and the reasons not to are manual alignment points and de-rotation. Both are real. Pick accordingly.