Step 1

The first step is obviously to create your image. For this tutorial, I used a image with a size of 1280×800.
Once you’ve created your image, create a new layer, and fill it with black. This will be the background layer.

Step 2

Now, create another layer, and also fill it with black. This will be the layer which contains the stars.
We need to add our stars to this layer, obviously. For this, go Filter -> Noise -> Add Noise, and use the settings shown below:

Step 3

The starfield currently doesn’t look much like a starfield, so let’s fix that. Select the layer with the noise, and apply a 0.4-0.6px Gaussian Blur to it. (Filter -> Blur -> Gaussian Blur)

Step 4

Now that the noise looks a bit more like stars, we need to remove quite a bit of the noise to achieve a more realistic star look. To do this, we need to play with the layer’s levels (Image -> Adjustments -> Levels).
Apply the settings shown below:

Step 5

To give the field a bit more of a random look, grab your eraser tool (Soft Round, 200px, 40% opacity), and go around the star layer removing random areas.
Next, we need to clone some of the stars, to give them more depth. Grab your clone tool (Soft Round, 200px, Screen Mode), and clone random areas of stars, so some parts of the image have more stars then others.

Step 6

Next, create a new layer on top of all the others, call it “clouds”. Fill this layer with some clouds (Filter -> Render -> Clouds), and set it’s blend mode to overlay.

Step 7

Now, below the clouds layer, create a new layer, and call it “Nebula”. Then, grab the gradient tool (Radial, #003d8e to transparent), and create groups of gradiented circles. Then, grab the eraser tool again (Soft Round, 200px, Screen Mode), and erase random parts of the group.
Then, set the opacity to about 45%.

Step 8

Repeat step 7 until you have a number of nebulas that you like. Change the color, the opacity, or even use a textured brush.

Step 9

Now, we need to create the extremely bright stars, which is actually very easy to do. Create another layer, and make sure it is on top of the nebula layer. Fill it with black, and set the blend mode to screen.
Then, go Filter -> Render -> Lens Flare. Apply as many as of these as you want around the image, changing the type of lens and the brightness.

Step 10

Now we need to create a color effect over the stars. For this, create a new layer below the nebulas, but above the stars. Fill it with black, and set it’s blend mode to overlay. Then, set the opacity to about 22%. Next, fill the later with a a rainbow gradient. This applies a cool colorized gradient to the stars.

That’s it, we’re done! Remember to try different colors and brushes, to attain hundreds of unique effects.