Focal Pointe Observatory
Astrophotography by Bob Franke

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Star Repair w/ PhotoShop

With LRGB imaging processing, we use one layer for the luminance data and another for the color. It is common to blur the color data for reducing noise. Blurring the color data reduces the color differential and detail in the final image. We can take advantage of this reduced color detail for repairing problem stars.

This demonstration uses a narrowband image. Therefore, we use the same data for both the luminance and color layer. See Image 1.

Image 1

Use the Magic Wand for selecting the stars. Set the sample size to a 3x3 average and the tolerance to 5. Image 2 shows six selected stars.

Image 2

To clean up the stars, expand the selection by 8 pixels, set the feather radius to 3 and execute a Gaussian Blur with a radius of 3 pixels. See image 3 for the result.

Image 3

Image 4 shows how the Gaussian Blur reduces color saturation in the area of the stars. Increasing the saturation to 15 or 20 can return a star's color.  This was not necessary in this example.

Image 4

A final suggestion is to set up a PhotoShop action. This makes the process work with just two mouse clicks. One click to select the star and a second to execute the action.