But I could even do that in Photoshop without the photo! It wasn't dramatic enough as a moon shot, and I spent a pointless twenty minutes looking for a tree silhouette in public domain stuff on line ... then realized I have lots of tree silhouettes in my own photos.
In my Flickr account, I found one that seemed to fit the bill: a nice silhouette, a sky that was not too busy, colors that were simple.
Then I bled the black out of the moon shot, (trying to get a blue background instead of a black one) and turned to the other photo. I inverted the colors on the tree shot to make the branches come out white, selected the blue color from the bottom of the inverted pic -- a nicer blue than I came up with on the moon pic -- and spread it upward on the sky of the tree image. Back to the other pic again. I selected the sky on the moon shot with the "Magic Wand" tool, inverted the selection so that I got only the moon, and pasted it on the tree shot. Yeah.
I did some tinkering with the blue colors and the "Paintbrush" tool (making it about 50% opacity and a fuzzy edge) and scrubbed at the sky a little -- I didn't want it perfectly homogenous, but didn't want a lot of variation, either.
By this point, I'd spent about 40 minutes from inception to a reasonable product. Four years ago, it would have taken me all day and a case of the hives to boot. Practice, practice, practice. Do, do, do. Dang, it pisses me off when good advice really does pan out if you take it. Could not my artistic ability have sprung forth fully-formed from the brow of Zeus and saved me all the sweat and nerves and twitches?
With the final image on the screen, I reduced the size, and got one of the best Photoshop images I ever thought I'd get.
My, that sure feels fine.