I used two photos of the recent supermoon and combined them. The result is OK (link below). I was unable to achieve a look I wanted, where haze causes darker areas of the moon surface to assume the same color as nearby sky, and only brighter areas of the moon stand out. I tried selecting the shadow areas and using "Color to Alpha" in GIMP, but the effect was very harsh. Any tips?
There are some variants on your approach which would be less harsh, although I'm not convinced that you'll get the effect you want without applying some kind of haze effect to the whole sky.
- Use your current approach and apply a curve to the layer mask to make it less noticeable.
- Change the layer mode of the moon to "Lighten only"
- Place a second copy of the sky over the moon with layer mode "Lighten only" and play with its opacity.