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I have learned a lot in the time I have been doing astrophotography. I know now that this is a challenging process that requires knowledge and experience in many areas which are new to me. Having succeeded in solving some of the basic beginner’s mistakes and having solved a bucketful of problems, I know that what I have learned can help you in your journey in astrophotography.
Astrophotography processing software includes stacking and then processing in a programme such as Photoshop. There are many different programmes and software that can be used. The image processing involves stretching the image, adjusting the level of the background, adjusting contrast and colour, and reducing noise.
On this page, I want to focus on what I have learned about astrophotography image processing. This will include the different astrophotography processing software I have used and what I think of them. As my astrophotography image processing skills develop, you can learn from my mistakes and solutions and then, hopefully, go off to explore new areas and develop your own imaging and post-processing style.
Astrophotography Processing Software I’ve Used
So far, I have found the following programmes helpful and will continue to use them:
- Siril (Free stacking and image processing)
- Sequator (Free stacking only)
- Registax (Free stacking of planets and online image processing)
- Deep Sky Stacker (Free astrophotography processing software that stacks your images)
- Pipp (a free programme that converts video to images for stacking in other programmes)
- Photoshop (I use the CC version, 2023)
Let’s look at each of these and how they can help you with the processing of your astrophotography images. Later in this post, I will also talk about other astrophotography processing software, such as Astro Pixel Processor and Star Tools, which I have tried but do not use at present. I’ll explain why.
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One problem I ran into early on was that my laptop was not able to run some of these programmes quickly and often crashed. I have discovered, for example, that Star Tools and Astro Pixel Processor, as well as Photoshop, needed more resources than I had on my laptop. I upgraded my RAM from 4MB to 16MB and replaced my hard disc with an SSD drive and now my laptop is fast and can handle these image processing programmes.
Adobe Bridge
One programme I have discovered recently is Adobe Bridge.
I really like this software for several reasons. First, it allows me to sort through my images and review them quickly to see which images I need to reject or accept. There is a handy zoom tool in review mode that shows me the existence of any star trailing and how bad it is. If it is too bad, I label it as rejected, and later can delete them or move them so that I have only good-quality images to stack.
Another feature of Adobe Bridge I use is collections. I can add any of my astrophotography images to my collections no matter where they are and they appear on the menu in the lower-left pane under collections. I don’t need to search for certain pictures anymore; they are all there when I want them.
Photoshop CC
I have been using Photoshop since upgrading my laptop and hoping it will take my editing to another level. Below is an early result when using Photoshop (second image) to edit an image processed in Siril soon after starting to process astrophotography images.
The Cocoon Nebula exposures of 60 seconds were stacked using Deep Sky Stacker and then processed in Siril. This resulted in image A. In Siril I did color calibration and stretched the image. Image B is the result of processing the image in photoshop to remove the noise, reduce the stars and remove the gradient.
I am sure you’ll agree that this image is far from perfect, but I can clearly see a difference in the clarity of the nebula.
I have also loaded the highly recommended Astronomy Tools Actions into Photoshop and I like the results I am seeing so far!
Below is the difference that using Photoshop and the Astronomy Tools made to this image of the Andromeda Galaxy from early in my astrophotography journey.
I have to say that I was not happy with this image and have struggled with it. I will come back to M31 again and try some experimentation to improve it. Bear in mind also that this was my first year of astrophotography and now I have improved both my acquisition skills and my post-processing skills so look out for updated pictures of this target again very soon.
Anyway, the original photo before processing in photoshop lacked details as you can see around the core and in the small neighboring galaxy.
The main reason why Photoshop helped to bring out more details in my shot of Andromeda is that it allows me to stretch the image, boost contrast and reduce the noise. Since this photograph was taken about a year into my Astro imagery journey, I have improved my image processing and photography skills and upgraded my equipment. Newer images of the Andromeda Galaxy that I have taken will be added to this site soon.
Image Processing Tutorials
Here are a few good tutorials that will help you improve your astrophotography image processing skills:
- Processing the Lagoon Nebula with Siril (2minutes 55 seconds)
- Removing Light Pollution in Photoshop (5:15) – an oldie but a goodie from Peter Zelinka.
These two tutorials have been chosen because when I was starting out they really helped me and also they are for two of the programs that I use.
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Image-Stacking Software
Astrophotography involves an important process called image stacking. If you don’t know what this is let me quickly explain.
I have taken many photographs of distant and very faint deep sky objects. When I look at one frame its hard to see any details at all, just a faint blur is usually all you can see. So how to go from this to a great astro image?
The process we use to take incredible pictures of distant objects in space is called stacking. By taking many photos of the same object and stacking them together the image becomes more detailed and less noisy. The more images you take, the better.
The noise in astrophotography images can really spoil the picture and hides details and colour. Stacking is important because it reduces the noise by a factor equal to the square root of the number of images taken. So, take 4 images and you halve the noise, take 9 images and you’re left with a third of the original amount of noise. That’s a reduction of 66%
Noise reduction is not the only important benefit of stacking many astrophotography images. You also boost the signal you want from your target so SNR (Signal to Noise Ratio) increases drammatically. The result is a higher quality image.
Also, stacking creates an average overall image and removes things present in individual frames like plane or satellite trails that often appear in several of my images through the night. With Skynet satellites making this problem worse, we can really benefit from stacking software which automatically removes these artifacts but adds more valuable signal to the stack.
There is a rule in astrophotography that the more exposure time, the more detailed and less noisy our images will be. The best way to increase overall exposure time is to take multiple images of shorter exposure time and stack them rather than taking one long exposure. This is much more practical than taking one shot for hours.
Nowadays I try to get 10-15 hours of total exposure time and I find it best to break that into 5 or 6 minute subs. When targets have very bright cores, or if it is windy, I tend to lower the exposure time and stack more frames.
Software is required to align and stack together many photos that we take of an astronomy target such as a nebula or a galaxy. Often, calibration frames, for example, dark frames, are added to the program, which uses them to extract some of the noise from the images and produce a cleaner-looking stack.
So, to summarize image stacking software is extremely important if you want top quality astrophotography images.
What is the Best Image Stacking Software?
The answer I give will only be my opinion, but I have tried most of the popular programs out there, especially the free ones. Of course, there are expensive options such as Pixinsight and so on, but why pay when there is good free software available?
I would say these are some of the best programs I’ve tried for stacking astrophotography:
- Deep Sky Stacker – very popular and does the job with some processing capability. Can also stack groups of images from separate nights. I find it a bit clunky and confusing to get the hang of.
- Sequator – I used this very early on when I first started astrophotography and liked the simplicity of the software. Very easy to use. Good results I thought until I did a direct comparison with Siril. I decided to use Sequator for widefield and Milky Way shots, perhaps comets too. I believe that there are better programs for deep sky objects. It’s a good program which allows you to align the stars in your images and freeze the background. very handy!
- Siril has been my first choice and I believe it is the best stacking software I have found. It is also free! It has powerful post processing components as well as the stacking. You must try it!
My choice of stacking software is Siril.
What is the best astrophotography processing software?
My software of choice for editing and processing my images is Photoshop. I find it easy to use and love the astrophotography plugins I use with it. It is considerably cheaper than other software such as Pixinsight and others, but I believe it does all that I need and more!
Once I have the stacked image, I open it in Photoshop and perform one or two stretches, level checks, and balance the colour in the image. This is followed by a workflow that includes contrast and brightness adjustment and noise reduction. The colour in the final image can be boosted using saturation and vibrance to taste. Some like very bright and colourful astrophotography images, but I prefer to tone it down a little to something more natural-looking.
There is really only one way to improve your image processing skills, and that is through practice. You can always stop, go back, and redo an image later to obtain a better result.
Conclusion
All in all, I have found the best tool for image stacking to be Sequator, and for processing the image, I prefer to use Photoshop, but many prefer to use Pixinsight, which is much more expensive and requires time to learn.
