Astrophotography software, and which one to open first

The short answer

• Deep sky, free, any OS: Siril.
• Deep sky, free, Windows, simplest possible: DeepSkyStacker.
• Planets and the Moon: AutoStakkert! to stack, RegiStax to sharpen.
• Nightscapes on a tripod: Sequator.
• Both kinds of target without assembling a workflow: Akastroid.
• Full control, and time to learn it: PixInsight.

Calibration, registration, stacking and a full set of post-processing tools, with a scripting language that can run a whole session unattended.

Install it if: A free starting point for deep sky on any operating system, if you are willing to learn the order the steps go in.

The catch: It does what you tell it and nothing you did not. The scripts in the manual assume you already know which one matches your data.

Loads lights, darks, flats and bias frames and produces a stacked master. That is its entire scope.

Install it if: A Windows beginner who wants one job done and is happy to finish the image somewhere else.

The catch: Windows only, development is slow, and it stops at the stack. The flat gray result still needs a second program.

The standard for planetary and lunar stacking: grades every frame of a video, keeps the sharpest, and aligns on a grid of points across the disc.

Install it if: Anyone stacking planetary or lunar video. It is free and it is very good at this one thing.

The catch: Stacking only. The result is deliberately soft and expects RegiStax or similar afterwards. No deep sky, and no macOS build.

Wavelet sharpening. Six sliders that pull detail out of a planetary stack at six different scales.

Install it if: The second half of a planetary workflow, after AutoStakkert! has produced the stack.

The catch: Unmaintained since 2011, and the sliders have no useful defaults. The result is whatever you dial in, including badly over-sharpened.

Gradient removal, plus optional denoising. It is not a stacker; it fixes one problem in an image you already have.

Install it if: Anyone whose stacked image has an uneven background from light pollution or moonlight.

The catch: One step of a workflow, so it is an addition to your shortlist rather than an answer to it.

Deep sky and planetary in one program: it measures your frames, decides the calibration, stacking, gradient, color and stretch for itself, and shows you the numbers behind each choice.

Install it if: Someone who wants a finished image from a night's data without first learning which of five programs to open in which order, and who wants to see what was done to it.

The catch: It makes the decisions for you by default. If you want to drive every decision yourself, PixInsight gives you more control and Siril is free.

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Stacks wide-field nightscapes, such as the Milky Way over a landscape, keeping the fixed foreground sharp while the stars are aligned.

Install it if: Camera-and-tripod nightscapes, which the telescope-oriented stackers handle badly.

The catch: Windows only, and it is built for landscape astrophotography, so it is not much use on a telescope target.

The most capable image-processing platform in amateur astrophotography, and the one many published images pass through.

Install it if: Someone past their first year who wants full control over every step.

The catch: Months to learn, and the interface assumes you already understand the mathematics. It is not a first program, and its own community says so.

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What is the best astrophotography software for beginners?

For deep sky on any operating system, Siril. It is free, actively developed and covers the whole workflow. On Windows, DeepSkyStacker is simpler but stops at the stack. For planets and the Moon, AutoStakkert! followed by RegiStax. If you would rather not assemble a workflow out of three programs, Akastroid covers deep sky and planetary in one and is free to try.

Is there free astrophotography software that is good?

Yes. Siril, DeepSkyStacker, AutoStakkert!, RegiStax and GraXpert are all free, and a large share of amateur images are made with the first four. What separates them from paid software is not quality so much as how much of the sequence you have to know before you start.

Do I need different software for planets and deep sky?

Traditionally yes, because the two need opposite things: deep sky stacks long exposures to beat noise, while planetary grades thousands of short video frames and keeps only the sharpest moments of seeing. That is why most people run DeepSkyStacker or Siril for one and AutoStakkert! plus RegiStax for the other. Akastroid does both, and detects which kind of data you loaded.

What is the best astrophotography software for Mac?

Siril, PixInsight, GraXpert and Akastroid all have native macOS builds. DeepSkyStacker, AutoStakkert!, RegiStax and Sequator are Windows-only. AutoStakkert! and RegiStax can be made to run under Wine, but that is one more thing to maintain.

What is the best astrophotography processing tool?

It depends which half of processing you mean. For deep-sky post-processing (stretching, gradient removal, noise and colour), PixInsight is the tool experienced imagers use and Siril is the free one that covers similar ground with a shorter menu. For planetary and lunar, processing means wavelet sharpening, and that is RegiStax or AstroSurface after AutoStakkert! has stacked. GraXpert does one job, gradient removal, better than most bundled tools. Akastroid keeps the job in one program: it grades, stacks, sharpens and finishes deep-sky and planetary data in one pass, on macOS as well as Windows.

What is the best astrophotography image processing software for a Mac?

Siril, PixInsight, GraXpert and Akastroid are the ones with native macOS builds, and the list is short because the usual planetary chain (AutoStakkert!, RegiStax, PIPP, WinJUPOS) is Windows-only, so Mac users run it under Wine or a virtual machine. If you shoot planets on a Mac, that matters more than which program stacks better.

How much should I spend on astrophotography software?

Nothing, until free software has become the limit. For most people early on, the limit is focus, guiding or light pollution rather than the program. Spend on the data first.