Bart Senior wrote:

2 points to you Doug

Yeehaw, does this mean I'm winning?!?



I'm not entirely sure I understand your method. But you hit thed key
points,
height of eye for the observer, and height of the light are both limited by
the curvature of the earth and the horizon--even if the light is luminous
enough to be seen at greater distances.

Right... in which case, you might see the "loom" of the light's glow over the
horizon. Very reassuring to see this!



I typically calculate the horizon for my height of eye, and also for the
light
based on it's height and add the two together, and check this against the
specs on the light, which is usually greater.

IIRC you should add the heights first, then calculate the horizon. There is an
exponent in the formula which will throw you off. I'm usually in a hurry and
just interpolate from the tables in the appendix....


Fresnel lenses are amazing techonology. Have you seen one up close?

Yes, been inside one of the big ones. They are amazing.

One of the mysteries of history is what happened to the Cape Hattaras lighthouse
Fresnel lens at the outset of the War of Northern Aggression... some
Confederates thought it would be a good idea to swipe it, since it was very
expensive and, in place, could only benefit the Union Navy. Sketchy research
indicates that they hid it somewhere far inland, possibly on a farm in Vance
County (which means it's most likely under Kerr Lake now). There are still only
a few 1st-order Fresnel lenses on US lighthouses, IIRC the Cape Hatteras light
was only given a 2nd-order after the war.

Fresh Breezes- Doug King