[ARC5] Blackout ; Lend Lease and ARC-5's (OT)

[Brian Clarke]

There is a simple formula for estimating the horizon from any height on the 
surface of the Earth. R (range) = sq rt [2 r x h], where r is the radius of 
the Earth and h is the height of the observer's eye above the Earth's 
surface. So, if you are in the crow's nest with your eye at 100' above the 
Earth's surface, and assuming the Earth's radius is about 4000 miles, then 
the Range to the horizon is 12 miles. It's just plain Pythagoras' theorem. 
If the working lights in the shipyard are some height above the Earth's 
surface too, then do another calculation for the horizon from the ship's 
lights - then add the two values of R together. So, if the shipyard lights 
were also at 100', then the lights would be visible from a 100' crow's nest 
from 24 miles.

73 de Brian, VK2GCE.

On Sunday, July 08, 2012 6:37 PM, Les Smith asked:


> Thinking more about this, (how far distance you could see the
> working lights in a ship-yard) I figure my memory is completely
> wrong here.  It would be difficult to see the sun two hours away
> (due to the curve of the earth).   It's good Henk isn't here,
> he'd box my ears for mis-quoting him.  Then I WOULD be sorry.
>
> 73
>
> Les
> [1]vk2bcu at operamail.com
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