The paragraph immediately before the Header What Makes the colours of a Rainbow.. in the first link which is the same one you provided. answers your question about when one can see the fuller arch.
quote:
We don't see a full circle because the earth gets in the way. The lower the sun is to the horizon, the more of the circle we see -right at sunset, we would see a full semicircle of the rainbow with the top of the arch 42 degrees above the horizon. The higher the sun is in the sky, the smaller is the arch of the rainbow above the horizon.
Alex
[This message has been edited by Alex K. Viefhaus (edited January 02, 2005).]
