Re: [APML] How far are light domes visible....

[Tim Povlick <potentate@cox.net>]

Chris & Jennifer Cook wrote:

>
> When all you have is empty, unpopulated relativly flat desert between you
> and a large city, it can be seen for a long way.
>
> Chris

I checked my book "The ARRL Handbook for Radio Amateurs" and they
give the formula, for radio waves at VHF as:

   d = sqrt ( 2 * h )

where D the distance in miles and  h  is the height above ground
elevation in feet.   In km and meters the formula is:

  km = sqrt (17 * Meters)


for a person  5' 6" tall standing at the beach  the horizon is at
 3 .3 miles (which agrees with what I have read else where)

For the problem at hand, the difficulty is deciding how far
'up' the light can go and still be bright enough to scatter
downward toward the observer.  If your on a hilltop say
2,000 feet about average terrain: the distance is 63 miles.

If light from a city goes as high as 12,000 feet and is still
bright enough to cause back scatter to the observer on the
hilltop, then the distance becomes: 155 miles.

----

Tim Povlick
San Juan Capistrano, CA


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