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Home » Astrophotography

Starry Sky Stacker Tutorial - Astrophotography Stacking on MacOS

Published: Feb 19, 2019 · Last update: Oct 3, 2025 · Author: Paweł Białecki · Leave a Comment

Stacking your astrophotography pictures is crucial to eliminate noise and reveal hidden details. But unfortunately, one of the most popular software for stacking, the Deep Sky Stacker, is unavailable for macOS (the former Mac OS X). Should we, the Mac users, be sad because of this? Well, maybe, but we are certainly not lost. Other programs can do the job, just like the Deep Sky Stacker, or even better. In this post, I will show you one of the best astrophotography stacking software options for macOS - the Starry Sky Stacker.

Jump to:
  • What is Stacking in Astrophotography
  • Why Should you Stack your Astrophotography Pictures?
  • What is Starry Sky Stacker
  • How to use Starry Sky Stacker
  • Final Image
  • References
  • FAQ
  • Learn More
  • 💬 Comments

What is Stacking in Astrophotography

In astrophotography, stacking is a process of combining multiple exposures (all with the same settings - ISO, exposure time, aperture, etc.) into one so-called stack. In the stacking process, every pixel in the final stack image is created by averaging pixels from the proper places from so-called subs - single exposures, often called light frames. As a result, the stack has the exact pixel resolution, and before further post-processing, it looks almost the same as every single exposure it has been produced of.

These are two different images. On the left, there is a single light frame of the Orion region, unmodified in any way, straight from the camera (Fuji X-T20). On the right, there is a stack composed of seven light frames (this one on the left included) with the Starry Sky Stacker. Not much visible difference for now.

Why Should you Stack your Astrophotography Pictures?

It would be best if you stacked your multiple astrophotography pictures into one to improve the signal-to-noise ratio, which leads to removing unwanted camera sensor noise and revealing faint details on your images. Stacking is the foundation of a successful astro picture, and it's the first thing you should learn when you start doing astrophotography post-processing.

Single Exposure vs. Stacked Image

Exact pictures stretched and post-processed in PixInsight and Affinity Photo (best effort processing both). The Flame and Horsehead nebulae start to appear (the top-left corner), and the image on the right is a stack composed of only seven light frames. The recommended minimum to get an adorable astro picture is 20 - but the more, the better.

What is Starry Sky Stacker

Starry Sky Stacker is an astrophotography stacking app for macOS written by Ralph Hill. It has multiple functions for creating good quality stacks for further processing:

  • Combining single exposures using different algorithms (you can choose which one you want to use) - median, mean, max, or min.
  • Aligning your subs if they were not tracked accurately.
  • Estimating the quality of your subs and letting you decide which ones to use for the final stack integration.
  • Optionally using also dark and flat frames.

How to use Starry Sky Stacker

Prepare your TIFF Subs

Always use RAW as your camera format, not JPG. JPG is a lossy file format and doesn't preserve all that data that came from the night sky, and your goal is to reveal as many details as possible on your final image. To do that, always shoot and process your pictures in RAW or other lossless formats (like TIFF or FIT).

Starry Sky Stacker uses the TIFF file format for internal processing. Therefore, it's best to export your RAWs to TIFF with default values using some RAW processing software (like Capture One).

Load your Subs into Starry Sky Stacker

Select your subs and load them into the program. If you want to use darks or/and flats, check the "show image classification" tick. If you have only light frames, then leave them unchecked. After a few seconds (depending on the number of your subs and the power of your machine, it may be longer), you will see a screen like this one below. You can exclude some worse subframes (with passing clouds, e.g.), and after that, click "Composite."

Single exposures loaded into Starry Sky Stacker
Single exposures loaded into Starry Sky Stacker.

Tweak Composition Details

A composited stack image Starry Sky Stacker
Your stack is almost ready.

Images are aligned. Now you have to select the composition algorithm and optionally play with brightness and contrast settings. I usually use the median algorithm and leave brightness and contrast settings default (I do that kind of further post-processing in PixInsight and Affinity Photo later). Finally, click "Save" and choose your drive's final stacked picture location. Your stack is ready for post-processing!

Final Image

On an APS-C sensor, the Orion, Running Man, Flame, and Horsehead nebulae at 200mm focal length.

References

Starry Sky Stacker

Official developer page

Watch the Starry Sky Stacker developer's introduction to the program.

Other Stacking Software Options for macOS

PixInsight

FAQ

What is Starry Sky Stacker?

Starry Sky Stacker is astrophotography stacking app for macOS written by Ralph Hill. It has multiple functions for creating high-quality stack images for further astrophotography processing.

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Paweł Białecki, the author behind Astro Photons
Paweł Białecki

I'm Paweł Białecki - an astrophotographer and indie app developer who's been exploring the night sky for over a decade. Here on Astro Photons, I share practical guides, cosmic insights, and deep-sky photos to help you enjoy and understand our universe - no telescope degree required.

This blog is part of my personal mission to make astronomy more approachable. I write for beginners, hobbyists, and curious stargazers who want real, useful advice - not just textbook definitions. All guides are based on hands-on experience, actual night sky photography, and a genuine love for the cosmos.

Outside of astronomy, I also build digital tools and educational projects in other areas. One of them is System Formy - a Polish-language project focused on practical nutrition and realistic fitness for busy adults. Just like in astronomy, my goal is to simplify complex topics and turn them into clear, usable systems people can apply in everyday life.

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