Well, I wasn't going to comment, 'cos I LOVE this image, but (opens mouth, ready to receive foot)... On a clear day (you can't see forever, that's reserved for nights), the atmosphere reflects and refracts the sun's light, and the thicker the atmosphere, the greater the effect. The atmosphere reflects/refreacts most in the "red" zone and least in the "blue" zone (which is why the sky appears blue - mostly blue light getting through to our eyes). Since the atmosphere it thinner looking up than looking towards the horizon, the greatest effect of that is towards the horizon. The net effect is that the sky looks more grey (gray) towards the horizon, and more blue the higher you look. So, unless there are other (cloud/industrial) reasons, the sky should just shade upwards towards blue... So: May I suggest trying a sky which just grades upwards from blue/grey to a deeper bue?? Cheers, Diolma