Thanks guys, I am going to make some adjustments and rerender a few times. The render times are really nice around 30 minutes at 1200X1200 so it is easy to make changes.
Paul: The atmosphere node is at default as far as I remember, but the camera exposure is set to 16! There are more canyon walls in the background but the super high exposure burns everything out. There is no cloud layers or mist/fog or anything like that, everything is handled by the light.