Yes, you read the title correctly: we will be removing stars in this tutorial.
At this point, you're probably asking why we would want to remove stars if we've just travelled for hours to reach dark skies to maximise the number of stars we see.
Well, I'm glad you asked :)
If the Milky Way is our end game, we want to maximise the detail we get in the Milky Way core. At the same time, we're capturing 100's, if not 1000's, of stars in the sky as well. In fact, we can capture so many stars surrounding the Milky Way that the final image can look a bit busy, distracting from the Milky Way core (you can see this in the image below). We therefore want to reduce the number of smaller stars so the final image looks cleaner with less "noise", making the Milky Way core stand out more.
To reduce the number of these smaller stars and make our image look less grainy (or noisy), we will use a Photoshop filter called Dust & Scratches to remove these smaller stars. This tool works by modifying dissimilar pixels to achieve a balance between sharpening and hiding defects.
1) Open your image in Photoshop (see image above)
2) Select the Filter menu
3) Move down to Noise submenu
4) Select Dust & Scratches
Tip: always work on a duplicated layer of your original image, never work on the background/original image itself. This way you not only protect the original file, but can control the percentage opacity of the modified layer, giving you even more control in fine-tuning the image to the desired effect.
Once you have selected the Dust & Scratches tool, a small window will pop up, allowing you to control the radius (number of pixels associated with the size of the noise we want to hide) and the threshold (balance between smoothness and detail). For Milky Way images, you shouldn't need to increase the radius above 1 pixel. If you do you'll start to remove too much detail, making the image look blurry.
The threshold slider is used to balance the level of detail desired versus the smoothness of the image (see above image). Slowly increase the threshold slider, adding back detail until you see the small stars begin to re-appear in the image. Then move the slider back down until you are happy with the balance between the image smoothness and retained detail. I usually find between 20-35 levels works well for the Milky Way (see image below), but it depends on a number of factors, so play around with it and see what works best with your images.
I hope you found this article helpful :)
Please check out my other articles on my website, or send me an email letting me know what other photography problems you may have so I can put them into easy-to-follow tutorials like this one.