Originally Posted by
ROTD
Just cutting in half like that isn't going to work very well at all. Try some sort of transition between the two, gradient, slight color change, etc. Block colors like that next to each other doesn't work well. Sun needs a lot more contrast, since it's hard to tell what or where it even is. At the moment it wont look realistic because of the colors you have chosen. Something a bit less drastic would help you out a bit. Also, your original image is of fairly low quality, you should try to get a better image so you can work with it more and get closer to your desired effect.
A few tips if you don't quite know how you should go about fixing it:
Make the contrast consistent (don't change it so drastically and leave the original there, change all the contrast or use a dither of some sort to transition it cleanly between the original and the altered versions.
Take out the sun or get another image, light source and the angle of your sun do not match, and won't look realistic because of that.
Don't change sky color that drastically, you've placed blue, with almost it's direct opposite on the color spectrum. You don't want to do that. Trust me.
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That's probably it, post or send me a message if you need anything else. I might be able to help you out if I'm still on.