Right a quick tutorial on this enhancement. I rendered two images one with and one without the clouds. In photoshop I opened up the image without clouds and selected a soft brush for the dodge tool. I made the brush about 20% bigger than the moon and then just clicked a few times over the moon to increase its brightness and glow.

Next I took the image with the clouds and dragged it over the original as a seperate layer. I set the blend mode of this layer to overlay then flattened the image. The overlay really overdoes the contrast so I duplicated the flattened image opened filters and selected guassian blur. I set the amount at 12 , clicked ok then set that layer to screen with opacity set at 60%. Then I flattened the image again before wisping the edges of the clouds with a splatter brush selected in the smudge tool.

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