At 06:49 PM 6/20/03 -0700, Jim Lux wrote:
>Dacron fishing line works as an invisible guy... even something like nylon
>seine twine would probably work, and not be overly visible.
>Human eyes can resolve about an arc minute, so you can figure out how small
>something needs to be to make it invisible, given the distance (... about
>1/4000th of the distance, so 100 ft away, it needs to be 1/40th of a foot or
>smaller... 1/4" give or take)
Unfortunately, this isn't the whole story. I can see the 3/16" EHS guys on
my tower from over 200 feet away. Super good eyes? Nope -- it isn't a
matter of your eye actually being able to resolve the width of the guy
wire, but rather the contrast between the color and/or brightness of the
guy and the color and/or brightness of the background. The result is that
the "pixels" through which the guy wires pass have a noticeably different
*average* color and/or brightness than those adjacent to them, so you can
see the wire even though it is too small to resolve.
I didn't used to believe this until I saw 30-meter-resolution satellite
photos of the causeway across Lake Pontchartrain that clearly showed a
roadway whose width was much less than the system resolution.
Bottom line is if you want it not to show, you need to match it to the
background as well as you can. I've seen a 75-foot tower with TH7DXX that
you had to look three times to resolve against the forest background
because of a carefully applied coat of brown-grey paint.
73, Pete N4ZR
The World HF Contest Station Database was updated 17 June 03.
Are you current? www.pvrc.org/wcsd/wcsdsearch.htm
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