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Subhorizon halo challenge ; DO YOU FLY?
I guess you people fly sometimes. There is a less
known international challenge going on to photograph
for the first time all halo forms, which yet
have escaped the eye of camera.
The rare halos that are encountered above the horizon,
ie. on the sky are relatively well taken care
of. However the rare halo forms that are found under
the horizon (visible only from an airplane flying
above ice crystals or from high tower during low
level ice crystal display) are lousily covered.
Of the subhorizon halos by far the most common is
the subsun; simple reflection of sun situated as
far belove the horizon as the sun is above. Occasionally
the subparhelia are found some 22 degrees
on both sides of the subsun. This is much more difficult
to see, but is still among the relatively
easy subhorizon targets. Then I recently flew to
Alaska from Finland (Helsinki/Kopenhagen/Seattle/
Anchorage/Fairbanks) the subparhelia were visible
on only two occasions and their summed up visibility
was only some 20 minutes.
Subparhelic circle - a white ring of much resemblance
of its upper counterpart (parhelic
circle) is rarely seen. The first picture of it
I am aware of was published in Scorer's Cloud
Atlas of World (1972). After that one only some
half a dozen photos presenting that circle have
come about in the meterological literature. I've
newer seen the subparhelic circle myself, but for
example airline pilots probably see it several
times within one year.
THREE SUBHORIZON PHENOMENA TO CATCH
There is at least three subhorizon halo forms,
which are theoretically bright enough and obvious
to exist in nature, but which either have newer
been photographed or more probably: the photographer
has not understood the value of his shots and
thus these things have newer appeared in the atmospheric
optics journals or in halo books. These gorcious
challenges are the following;
- Sub-120 parhelia. Bright white spots 120 left
and right from subsun situated on the subparhelic
circle. This should not be immensely difficult and
thus its currently a disgrace that no-one has yet
come up with shots of this halo form.
- Sub-73 parhelia. Fainter spots of light, which
do not have bright enough counterpart above the
horizon, only here in "downstairs". Newer observed.
- Subcircumzenith arc. Found surrounding the nadire
and thus a very difficult target from an airline
plane. But from a small aircraft with the pilot himself
determined to catch this nature phenomenon
for the first time ...it should work out eventually.
QUESTIONS
Do you have already any material like this (at least
subparhelic circles?) hidden in your drawers? Do you
know any small - less known - aviational magazines
which might have published big subhorizon halo displays
? Books by Greenler R. (1980; Rainbows, Halos and
Glories) and by Tape W.(1994; Atmospheric Halos) are
and the one by Scorer R. (1972 Cloud Atlas...) are at
the moment virtually almost only places to encounter
good photographs of these subhorizon effects.
I am making currently a book on halo phenomena. If you
have any good halo photos, or any other interesting
stuff to tell (of the subhorizon halos or other halos)
here is my contact information;
Marko Pekkola
Rautalammintie 5 A 9
00550 Helsinki
Finland
tel: +358-0-765196 / +358-79-530304 (15th July-15th August)
fax: +358-0-657728
e-mail: marko.pekkola_at_helsinki.fi
By the way, thanks for Michael Boschat of the sprites
messages. I for one vote these as the most interesting
mails yet in this news group.
Regards, Marko
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