A tip to get rid of the lines in the sky is to create an image 1024x512 pixels and insert a guide at 512px, paste your sky in but make it less than 1024 pixels then copy and flip it horizontally, then you can blur them together using the clone tool and merge them. Then use the Crop tool to make two 512x512 images. This way you should get no lines, I have done this to good effect in my later skylines (i think
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