An Introduction to the Secret Weapon for Amazing Milky Way Shots – Stacking

You’ve spent countless hours planning and obsessively checking the weather to go out and capture what you hope will be an epic Milky Way shot. You’ve got a great location, a killer composition and took the time to carefully dial in your focus and camera settings. You get them home and realize that there is just too much noise for there to be a good image. What went wrong? How do people get these epic, low-noise Milky Way shots?

Well, one option would be to use a star tracking setup, but this is expensive and complicated to learn. An alternative, however, would be to use a method called stacking. Using this method, we can shoot the Milky Way at extremely high ISOs and end up with a final image that has little to no noise.

The best part? This works regardless of rather or not you’re shooting on a low-end, crop-sensor DSLR or a multi-thousand dollar pro-body!

Before you start stacking those Milky Ways you should probably learn how to determine the best shutter speed to use!

An Overview of Stacking

Okay, so hopefully my little sales pitch above has you nice and interested in learning how to do this technique. Before we actually dive in, though, let’s take a moment to just take a look at what stacking is. 

When we shoot the Milky Way, we, of course, need to capture as much light as is humanly possible. Two of the ways to achieve this is by shooting with our lens wide-open and using a slower shutter speed, but this will only get us so far. We inevitably have to shoot at a higher ISO. Not too surprisingly, this results in quite a bit of noise. How much noise depends on the camera, but here is an example from a Milky Way shot I captured in the Red River Gorge.

Example of the noise you get without stacking milky way images.

 This frame was shot at ISO 6400. Looking at just this single frame you might think that there’s no way you could get a usable shot with any detail, but just take a look at the final image (note, the foreground was shot hours before the sky during blue hour and blended in later).

Example of the noise reduction you can achieve through stacking.

Now, the post-processing obviously plays a huge roll in the differences between these two shots, but the big thing I want you to pay attention to here is the lack of noise in the final result. This is purely from image stacking, not from any sort of other noise reduction techniques. 

How Image Stacking Works

To stack images, we will use a special piece of software. For this tutorial, I will be using an app called Starry Landscape Stacker, which is, unfortunately, a MacOS only app. It’s said that Sequator is a good Windows alternative to Starry Landscape Stacker, but I’m yet to get a result out of it that I’m happy with. If I ever do I’ll write up a tutorial of how I did it.

Anyway, for stacking to work you take multiple exposures of the sky (we’ll get to that in a moment) and load them up into the stacking software. The software will then align the separate frames and apply what’s known as a median noise reduction filter. 

In doing this, the software is able to isolate out the noise patterns and output a resulting image with greatly reduced noise. This is, of course, a gross over-simplification of how the software works, but this isn’t meant to be a computer science lecture 🙂 

So, let’s quit jabbering about stacking and take a look at how to actually do it!

Shooting the Sky

Note: I’m not going to go into any detail as to how to shoot a decent foreground for night shots in this tutorial. This is simply meant to be an introduction to the stacking process. If there’s demand for such a tutorial I can create it as a separate post. 

Before we can worry about loading our images onto the computer to stack them, we need to first take a look at how to photograph the sky for this technique. It’s actually virtually the same as shooting it for any other technique. 

The first thing you need to do is set up your camera settings to get a correct exposure of the Milky Way. Again, the process of doing this is outside the scope of this tutorial, so just let me know if you’d like me to do a separate write up on how to do this.

So far, everything is the same as it would be for any other Milky Way shooting technique. The difference here, however, is that you are going to take multiple shots of the sky, back-to-back. The more shots you get, in general, the more you’ll be able to reduce the noise later. I’d say 10-15 frames would be ideal. 

For reference, I used 10 frames for this final result:

Half Moon Milky Way

That’s really all there is to modifying your shooting technique to account for stacking! The best part is that we can even shoot at higher ISOs than we might otherwise using this technique. The real magic, however, comes from the stacking process itself.

Stacking the Images in Starry Landscape Stacker

Now that we’ve got our images, it’s time to start the stacking process. To start things off, I import my photos into Lightroom and do a very basic edit on the first frame of the Milky Way. This is meant to be a very basic edit to fine tune the exposure, contrast and white balance of the Milky Way. For reference, here’s the basic edit I did for the above shot:

Basic edits performed on the milky way images
These are the only edits I did to the Milky Way in this pass. You want to keep things simple at this stage.

Once you get your basic edit dialed in, select all your Milky Way frames and select the ‘synchronize’ option in Lightroom to sync all the edits you just made.

Sync settings in Lightroom.
Sync your settings in Lightroom.

Once your settings are synced, select all your frames and export them as TIF files. The settings you want for this export is a full resolution, 16-bit TIF file. Make sure you export the images with all the metadata, since Starry Landscape Stacker uses some of this information to help it align the frames. Export them to a folder so you can easily locate them again. 

Export from Lightroom for stacking.
Make sure you don’t resize the images and keep all the metadata intact.

Now it’s time to head into Starry Landscape Stacker and start the stacking process.

Starry Landscape Stacker

When you first open Starry Landscape Stacker, it’ll open up a dialog to open your images. Simply navigate to and select all your frames (in my case there are 10 of them) and hit open. Note, you can select multiple files by command clicking them. 

Open your images in Starry Landscape Stacker.
Select all of your frames to open them in Starry Landscape Stacker.

The app will then proceed to start reading your images and open them up. The view you’ll be greeted with may seem chaotic at first, but I promise you it’s quite simple.

The initial view after loading your frames into Starry Landscape Stacker.
The initial view after loading your frames into Starry Landscape Stacker.

You’ll notice a couple things about this view. Number 1, there are a bunch of red dots all over your image. These are points that Starry Landscape Stacker uses to help it align the images and detect the sky. We will be refining these momentarily.

The other thing you’ll notice is that the image it is displaying is extremely blurry. This is because it’s currently showing us an unaligned composite of our images. This will make it difficult to do what we need to do, so let’s instead use the Current Image dropdown in the lower left-hand corner to select a single frame to work with.

Select a single frame in Starry Landscape Stacker.
Select a single frame to make things easier to work with.

Now it’s time to refine those red dot points we mentioned before. It’s best to take some time to really refine these since this is how Starry Landscape Stacker not only aligns the images but also how it isolates the sky. 

The first thing we want to do is remove the dots that it erroneously placed on the foreground. We can do this by selecting the Erase Red Dots option to the left and simply painting over the dots that appear on the foreground. We only want these dots to be in the sky.