The Ever Elusive Green Flash...
an Atmospheric Event!
This photo was taken from Torrey Pines, California on
Jan. 7, 1996 by Andrew T. Young
Like many seaside communities, Naples resident's and
visitors alike, flock every evening to the beach in hopes of witnessing
one of nature's most elusive phenomenon...the
green flash!
Like many Neapolitans, I wanted to learn as much as possible about
the green flash, in hopes of someday, not just chasing, but actually
catching a green flash. I've put together some information that I hope
will aid you in finding your own "green flash". Good Luck!
What is the "Green Flash?"
The green flash is an atmospheric refractive phenomenon where the top
edge of the Sun will momentarily turn green.
The basic cause for the green flash is that refraction bends the light
of the Sun. The atmosphere acts like a weak prism, separating the light
into different colors. Bluer light is bent more strongly than red light.
However, the amount of refraction even at the horizon is quite small:
only a few seconds of arc (one second of arc is 1/3600th of a degree).
This effect is magnified by the atmosphere itself. Layering in the atmosphere
causes an effect similar to a horizontal cylindrical lens: the separation
of the color bands is exaggerated in the vertical direction, so that
the separation can be up to several minutes of arc.
What to look for:
A major problem for people who have never seen a green flash is not
knowing what to look for. Flashes are not always green; they are not
a "flash" in the sense of a sudden burst of brightness (except
at sunrise). They do not (usually) light up the sky, but are often small
and inconspicuous.
Location, Location, Location
If you want to see green flashes, you must be in the right place. The
major difficulty that people have in trying to see GF's is to insist
on standing someplace where green flashes are almost never visible.
Rule #1
An apparent horizon must usually be formed by some obstacle lower than
your eye, of course, the ocean meets this requirement perfectly.
Rule #2
The second important requirement is for reasonably clear air. If the
air is full of dust, smog, or haze, there won't be enough green light
transmitted at the horizon for you to see a green flash.
Rule #3
Finally, because most green flashes are pretty puny, it helps a lot
(especially if you are a beginner) to use a little optical aid: binoculars,
field glasses, even opera glasses will do. Even a little magnification
is a big help. (After you've seen several flashes and know what to look
for, you'll learn to recognize some of the smaller ones even with the
naked eye. But you might as well make it as easy as possible to start
with.)
But, be careful. The sun is safe to look at even with binoculars, when
it's right down on the horizon. But it's a lot brighter just
a few minutes earlier at sunset, or a few minutes later at sunrise.
The brightness changes by a factor of two every minute near sunrise
and sunset, so an error of just a minute or two can make the difference
between eye safety and eye injury. Be sure your horizon is really lower
than where you stand; and don't look at the Sun when it's more than
its own diameter above that low horizon. If your thumb, extended horizontally
at arm's length, can cover up the Sun while touching the horizon, the
Sun is low enough to look at safely.
A sensible rule is: If the Sun is too bright to look at comfortably,
don't look at it!!
Information provided by: Mount Wilson
Observatory, Andrew T. Young, copyrighted 1999
Disclaimer: Ruth G. Bethem and Downing-Frye
Realty do not endorse and are not responsible for any information contained
within. All information deemed reliable but urge any person looking
for a green flash to verify by their own means and to use caution and
good sense in protecting their eyesight. This is for general information
purposes only.
RUTH BETHEM, ABR, CRS, GRI, Realtor®
Premier Sotheby's International Realty
4001 Tamiami Trail N, Suite #102
Naples, Florida 34103
Phone: 239-777-7007 or Toll Free 877-777-7545
Information deemed reliable but not
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