The lunar color saturation process brings out subtle differences within the lunar landscape. The next step in the lunar image processing workflow is to increase the contrast of the structures within the image.

To do this, we use the Local Histogram Equalization process.

Moon before Local Histogram Equalization
Starting Image
Moon after Local Histogram Equalization
Ending Image

Local Histogram Equalization

Using local histogram equalization is a easy and fast process. It is useful to use the live preview as you adjust the settings.

Because I’m dealing with a 30% illuminated moon, I’m going to slightly increase the brightness, which will help enhance the color we will add later.

Local Histogram Equalization
Local Histogram Equalization
Moon - Local Histogram Equalization
Moon – Local Histogram Equalization

For the settings, the live preview will help nail down the best for your image.

  • Kernel Radius: Determines how large of an area to use to calculate the histogram. Start with 100 and work up to 300. Usually deep sky images are around 150 and lunar are closer to 200.
  • Contrast Limit: A value of 1 is no change. Usually 1.5 to 2 works well.
  • Amount: How much will the new image be blended with the old. A value of .5 to .75 works well.

What’s Next

This concludes the PixInsight workflow for lunar images. Additional items can be done depending on the outcome. This could include

  • Adjusting saturation with Curves Transformation
  • Preparing the image for publication by using