Star Color Enhancement by Jerry Lodriguss
http://www.astropix.com/HTML/J_DIGIT/STARCOLR.HTM

Summary: Select background, invert selection, remove target object(s), copy to separate color layer, saturate, smooth, merge.

Star with the image already open.

  1. Make the Layers Palette visible: Window > Layers
  2. Select the Stars in the image
    • Set the Magic Wand set to a tolerance of 10, with Anti-Alias checked on, and Contiguous not checked and Sample All Layers not checked.
    • Click on an area of blank sky background with the Magic Wand tool.
    • Select > Inverse to select just the stars (the Ring will be selected too). [Vary the tolerance or use Select > Modify > Enlarge, Contract, and Feather to fit the selection to the stars. You may want the selection to include more than just the star.]
    • Change to the Lasso tool. Set the feather to 0 pixels and check on anti-alias.
    • [Remove the target object from the selection:] Hold down the Alt key, left-click and carefully drag the lasso tool around the target to remove it from the selection. [ JL says to right-click for this, but that may be a difference between PS versions.]
  3. Copy stars and paste as new layer: Edit > Copy, Edit > Paste.
  4. Click on the star layer to make it active in the Layers Palette.
  5. (Optional) Open Curves and near the white end create a mild downturn to change saturated stars into bright gray stars. Then apply a weak Gaussian blur. This causes some of the star's halo where it wasn't orginally saturated to spread toward the stars' centers, carrying color information inward. You can play considerably with this step, expanding or contracting the selection areas, introducing feathering, and modifying the Gaussian smoothing radius.
  6. Image > Adjustments > Hue / Saturation, increase saturation of star layer to +95. [You may choose a lower saturation, or use the Edit > Fade... feature.]
  7. Blur the Star Color Layer: Filter > Blur > Gaussian Blur > Radius 1.0 pixel.
  8. Change the blending mode of the star color layer to "Color"
  9. Flatten the Layer: Layer > Flatten Image.
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