Deep Sky Stacker: Transform your Deep-Sky Pictures!

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Deep Sky Stacker is absolutely free. How can it help you with your astrophotography? Let’s find out.
If you want to photograph deep-sky objects you have a big challenge ahead. Take one long exposure photo and you’ll see a lot of noise and not much signal. In other words, a pretty poor image. How do you fix this?

The answer is to take many photographs and then stack the images together. This where Deep Sky Stacker comes in. DSS will stack images for you and allow you to do some quick processing and editing before you move into your image editing software.

In this post we’ll take a look at how you can use Deep Sky Stacker to create amazing astrophotos with incredible detail like the image below:

Black Eye Galaxy stacked image

The above image is of the Black Eye Galaxy. This was created from more than 300 images stacked together.

What is Deep Sky Stacker?

Deep Sky Stacker is one of the most popular stacking tools that astrophotographers use. It doesn’t cost anything and can sort your images and rank them in order of quality. After stacking it allows you to make some adjustments and stretch the image if you wish. There are many other features which we will come to shortly. Best of all, DSS is easy to use and quite quick to run.

Why Use Deep Sky Stacker?

In addition to what we have said above, deep sky stacker enables you to do the following:

  • Align your images
  • Stack images together so that noise is reduced
  • Use your calibration frames as you stack (dark, bias and flat frames).
  • Make it possible to create a clear image by stacking shorter exposures.

Deep Sky Stacker is not the only program that does this, for example, I also like Siril which is also free and does many of the same things that DSS does.

If you were to do the above steps manually it would be both very difficult and it would take a lot of time. Deep Sky Stacker makes these steps easier and more accurate.

How does DSS work?

Now you know how useful a program like Deep Sky Stacker is, let’s look at how it works.

First it aligns your images by matching stars in your picture. It works out how each frame has moved from a reference frame. Once it has done this, it places each frame perfectly on top of the others and averages out the image. This process of averaging increases the signal to noise ratio. Both the noise is reduced and the signal becomes clearer. This increase in signal to noise ratio enables the details of your object to be revealed in your final image.

The improvement in signal to noise ratio increases with the number of pictures you take as follows:

Increase in signal to noise ratio is proportional to the square root of the number of images.

In other words, taking 100 photos would increase signal to noise ratio by 10 times.

Taking 50 photos increases the signal to noise ratio by 7 times. Just 10 images will improve it by 3 times. In other words, the more images you take, the better your final astrophoto will be.

Taking calibration frames also helps. Bias and dark frames can be subtracted from the image to remove noise created by your camera and by temperature in the sensor. Flat frames can remove dust and stray light in your optics by subtracting this from your images.

How to Use Deep Sky Stacker

I’m going to run through the steps you can follow to get the best out of the program.

  • Install the software from this site
  • Open up your images in deep sky stacker by clicking on Open Picture Files
  • Add your calibration frames
  • Register the images by checking them all and click register images.
  • In the register settings tab you need to set the star detection level so it detects enough stars.
  • Check all your settings. Get help with these settings and learn how to set everything up.
  • Stack the images
  • Use the software to do some processing if you want or go to your processing software. I use Photoshop for this but you can use an alternative such as Gimp (free) or Pixinsight (paid).

That’s basically all there is to using Deep Sky Stacker to stack your images. If you need more information then click the above link, (get help with these settings), to learn more about how to use the program.

I did use a number of stacking programs and found that DSS was one of the best I tried in terms of the results. It was also quite easy to use. I also like Siril very much and do not have any complaints about it at all. I found one or two things difficult in DSS including the star detection sometimes not working for me. Now I realise that this was probably due to my inexperience and the lack of quality in my images rather than the program itself.

Tips for getting the best results with Deep Sky Stacker

These are a few essential tips to make sure you get the most out of the software:

  • Check that a sufficient number of stars are detected in your images. These are used to align the images properly.
  • Make sure that you shoot your pictures of deep-sky targets in RAW or FITS format depending on what your camera outputs.
  • Your final stacked image should be saved as a .tif or .fits file. These file types contain more information and the best for further processing.
  • Use the automated calibration feature which produces the best image with the least amount of noise.


I hope that you now know how Deep Sky Stacker can help you with your astrophotos. Stacking is a process that all astrophotographers need to use, so why not try using this software? It is a reliable and very popular choice, so I don’t think you can go wrong. I have had some issues using this program but it is easy to find solutions online because so many people use it.

Good luck with your imaging! I’d love to get your comments below, especially if you have any advice or suggestions how best to use this program.