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 (download on the Mac App Store).
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.
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
Single Exposure vs. Stacked Image
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."
Tweak Composition Details
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!
Starry Sky Stacker
Other Stacking Software Options for macOS
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.