How To Stack Milky Way Photos

By | 21/10/2022

An essential part of an astrophotographer’s processing toolbox, the
role exists in most processing software, including Adobe Photoshop and GIMP.

can be used to stack multiple image files, a technique that reduces noise (unwanted artefacts) in the terminal image.

It also allows u.s. to make gradual enhancements to our image files along the fashion.

You tin find out more about this process in our guide to astrophotography stacking.

As the
role provides the ability to delete modest processing errors at whatsoever stage of our edit, information technology means we don’t have to kickoff again if we brand a mistake.

Here we’ll show y’all how to use
in Photoshop to stack and process an image of the Milky Mode to bring out its wonderful, starry particular.

For more advice, read our guide to astrophotography and our tutorial on astrophotography prototype processing.

Milky Way stack layers before

Our initial image of the Galaxy is full of unwanted particular, which we will remove in ‘Layers’. Credit: Charlotte Daniels

Open your prototype files

Nosotros start by opening the image files that we want to stack in Photoshop.

File > Open
and navigate to the image file location. To open up multiple epitome files in Photoshop, nosotros hold the
key and select all the required files from the file location, earlier clicking
Open up.

Photoshop then uploads each of the selected files in split windows.

Each of these files volition exist used to form layers inside our stacked image. The file on the far left of Screenshot ane – labelled
Offset image
in our example – volition class our base image.

We will copy and paste all the other epitome files onto this one.

Milky Way stack layers step 01

In Adobe Photoshop we can load our epitome files in separate windows, set to get stacked layers. Credit: Charlotte Daniels

To combine these files into a single image ready for stacking, first start with the file window to the right of the base image – this will become
Layer one.

Click on the tab for this image then press the
Ctrl and A
keys at the same time. You will now see the image highlighted with dashed lines.

Alternatively, you can click
Select > All
in the image window. By pressing
Ctrl and C, this image is copied (or click
Edit > Copy).

Next, click dorsum on the base image window, and press
Ctrl and 5. This will identify your first layer on top of your base image as ‘Layer 1’.

Y’all can now delete the window that yous copied this file from by clicking the
symbol in the corner of the tab and proceed onto the next image file.

Next, repeat the re-create and paste steps for all the paradigm files you wish to stack, so that these become layers on summit of the base epitome.

At present we need to merge these layers into a unmarried stacked file, reducing the number of layers to one.

Milky Way stack layers step 02

Highlight all the layers using the ‘Ctrl’ key to reduce the levels of noise (unwanted artefacts) Credit: Charlotte Daniels

To practice this, select every layer past holding down the
key while clicking each layer, and then that they are all highlighted (see image higher up).

Next, click
Layer > Smart Objects > Convert to Smart Object. Once Photoshop has processed this command, click
Layer > Smart Objects > Stack Mode > Median.

You lot’ll see the paradigm change equally the noise level is gradually reduced.

We tin now apply the
office in a slightly different way to edit this stacked epitome.

The most effective way to use
for editing is to create a duplicate of the preceding layer, so that nosotros can use a new layer to make a separate adjustment each time.

To do this, hold down the
Shift, Ctrl, Alt, N and E
keys simultaneously. You will at present see a new, identical layer class (encounter image below).

You tin can now select whatever particular from the
menu – for case
Adjusting levels, or
(which we have highlighted) – and make an alteration specifically to that layer.

Once satisfied with the adjustment y’all’ve made, use the mouse to right click on the layer and select
Merge Down. This will combine your adjustment with the layer.

Milky Way stack layers step 03

Fine tuning adjustments can be made, including ‘Opacity’. Credit: Charlotte Daniels

Adjust your edits

By creating a new layer before making a new adjustment, yous are separating your procedure into stages.

The advantage of creating these layers for all the fundamental steps is that you have the flexibility to become back to any point and quickly review all of your steps to see where something might have gone wrong, or to mark what you did right.

If y’all determine an adjustment has made a change that you don’t like, you lot can remove that layer by right-clicking on information technology with the mouse and selecting
Delete Layer.

If you feel the adjustment was slightly likewise aggressive, y’all can as well solve this by adjusting the
for that layer.

Just move the
slider to reduce the effect of the alteration. To ensure full command of your edit, repeat the above steps on every adjustment you lot make.

When you take finished, you can use the mouse to right-click on a layer and select
Flatten prototype.

This ensures the finished epitome is in a suitable format to export as a JPEG or TIFF file (click
File > Consign as…).

We now accept the completed epitome (below), where the Milky Way is revealed in all its celebrity.

Milky Way stack layers after

The finished image brings out the particular and outline of the Milky way as information technology arches overhead. Credit: Charlotte Daniels

Stacking Milky way images: 3 quick tips

  1. You lot can modify the effect of an adjustment layer past alteration the
    mode; popular types are
  2. Try
    Hide All
    Reveal All
    masks, where each adjustment layer is practical to the image.
  3. Use the
    icon next to each layer to establish whether your most recent layer has improved the astro image before keeping or deleting.

This guide originally appeared in the Jan 2022 issue of

BBC Sky at Nighttime Magazine