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As I said, I simply reworded as best I could what was already there.  I understood this to mean that because the amount of water droplets visible along the line of sight below the horizon is limited (before you reach ground), the amount of light refracted is insufficient to be noticeable.  Above the horizon, looking up into the sky, you don't have this restriction.   This is why viewing from a high vantage point allows for more to be visible at a greater angle.  Again, if you dispute this logic feel free to reword or remove (as I originally did).  (Talk) "