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[TowerTalk] Visual Acuity & Shadows

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Subject: [TowerTalk] Visual Acuity & Shadows
From: (Jim Stahl)
Date: Fri, 19 Mar 99 13:25:40 EST
I doubt that a definitive no-see distance can be established,
considering such things as sunlight reflecting off guy wires, etc.,
which can't be easily quantified.
Last fall while atop W8KIC's 150 foot tower I was noticing the
shadows cast by the tower, and how they became less distinct as
they extended onto the neighboring property.  It occurred to me
that at some distance, the angle subtended by the tower members
becomes less than the angle subtended by the sun, and hence there
would no longer be a complete shadow cast by the tower.
I didn't follow up to calculate the numbers, but is some astronomy
type or otherwise ambitious person has the sun's angle it becomes
simple trig to get the no-shadow distance.  Keep in mind that the
moon has to block quite a high percentage of the sun for a solar
eclipse to be noticeable.
I hope this could be a useful point for someone involved in a tower
73   -    Jim    K8MR  

Jim Stahl
Basic Amateur Radio Frequency, BARF-80 +1 (440) 237-8208
"Totally devoted to Amateur Radio" - 24 Hrs a day 8/N/1 28.8k-1200 baud

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