First , I used this beach view photo 
I erased the sky in this photo

I places it by nighty 

I shosed this moon photo becaus of it's darken and lighten parts to place the other moon in the night sky photo
just select this moon by using Elliptical Marquee tool in Photoshop

then move it to your own disighn , then create another wight sphere shape and let it's layer be after the moon layer and add out glow effect , then change the mode of th moon from normal to pin light to make this result 

then there is my sketch I have collored it by using illustrator 

Don't forget to change the mode of the beach vew and the charachter by using Image < adjustment < matching color , and the source the blue night sky , plus use the black gradient  and macke it crate clipping mask on the character layer , and also wight gradiant in the other side  at the same layer caracter clipping mask but decrease it's opacity .

then in the layer caracter add the drop shadow effect , then in this layer effect press right click and chose create layer to control the drop shadow as you can see the result