The photographer who took this photo openly said "I've been borrowing nebulae from nasa hope they dont mind! This was originally shot in broad daylight" on his Flickr page. This means that he changed the background from day to night using gimp. The photo itself is really cool - except for the shadows of the trees shown on the trail. Those shouldn't be there, right? Trees don't cast shadow - at least not like that at night. What could you have done of you were making this edit to remove those shadows from the ground? Well, you probably could use an overlay to make the specific parts of the ground darker, or simply take this photo at noon, when no shadow is cast

What would help make selecting the sky to replace if with the starry sky easier? Hands down, shooting the photo in RAW would have helped, because that would give you the chance to create a very accurate layer mask to keep as many of your original tree branches as possible.

One other thing to note about this photo is the interesting color change that was applied to the top of the tree. I like it personally, but how would you add those to the tree? I'd probably mask off the tips of my tree so that my darken layers wouldn't make them dark, and then add a few dark pink overlays on the trees to give them that color.

Unless the moon is up...
Or wait for some slightly overcast day

Uh? Raw mode doesn't give you more pixels, and once in Gimp it doesn't give you more bit depth.

that's why I said "like that." I don't think the colors would look quite like that, do you disagree?

Yeah, that works too...lol.

You can edit the photo in UFRaw and transfer the photo to Gimp though. Using this, you can create some pretty good masks by making some adjustments to the curves like I did in my Gimp Zombie tutorial.That's what I meant.

Here's my go at it. It doesn't look nearly as nice as the image in the first post. I, too, borrowed from NASA and stole Centaurus A from them. Centaurus A

Original image: Bare Trees

Neat! It's a pretty cool effect. I'd like to try it sometime...I'm just so busy all the time :/

Yes I disagree. Colors look like whatever the color temperature setting make them look like. Our eyes become almost color-blind at night, with the reds going off first, but the camera sensor doesn't.

You can edit the photo in UFRaw and transfer the photo to Gimp though. Using this, you can create some pretty good masks by making some adjustments to the curves like I did in my Gimp Zombie tutorial.That's what I meant.[/quote]Yes, but from JPEG you make the same masks, shooting raw has nothing to do with that.