Big Dipper using Gaussian Blur
Astrophotography,  Photo Processing

Night Sky Photography – How to Increase the Size of the Stars

Normally in night sky or astrophotography the goal is to get pinpoint, small stars.  The smaller the stars, the more they are in focus.  However, there are times you want bigger stars in order to highlight them. 

Making a constellation stand out in your photograph is one example where you want to highlight certain stars.  In this photograph, I wanted the big dipper to be the subject of the photo and stand out from the other stars.  This can be quickly and easily done in Adobe Photoshop. Here is how I did it.

Big Dipper, Starry Sky Autofocus, Tripod
Big Dipper Before Image

Steps to Increase the Size of Stars in Adobe Photoshop

Note: This photo was edited on a Mac.  For a PC, use the Control key instead of the Command key and the Alt key in place of the Option key.

  • Open your photo in Photoshop
  • Create a duplicate layer (Command J)
  • Create a black layer mask (Option + click Add Layer Mask icon)
  • Select your mask and the paintbrush tool.  Make sure the foreground color is set to white and the opacity is 100%.
  • Set the paintbrush size a little larger than the star and click over each star that you want to make bigger.
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Editing a Mask to Make Stars Bigger
Editing a Mask to Make Stars Bigger
  • You can check your mask by option clicking on the mask. 
  • Click the layer icon instead of the mask
  • Go to Filter Menu > Blur > Gaussian Blur.
  • Set the Radius to around 1.5 or 1.6.  Larger depending on how big you’d like to make the stars.
Using Gaussian Blur on Stars
Using Gaussian Blur on Stars
  • Gaussian Blur will make the stars dimmer.  Create a new Brightness / Contrast Adjustment Layer.
  • Copy the mask from the Gaussian Blur Layer (Option + drag layer mask over Brightness / Contrast Layer Mask).
  • Increase the brightness of the Brightness / Contrast Adjustment layer.
  • If it’s not bright enough, duplicate the Brightness / Contrast Adjustment Layer (Command J).
  • Flatten the image (Layer Menu > Flatten Image), save, and close.
Big Dipper using Gaussian Blur
Big Dipper After Using Gaussian Blur

Written by Martin Belan

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