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Hello Chuck and all others,
Sun dogs (other names are parhelia and mock suns) is one of the most usual
haloforms one can see. Here in Finland one can see parhelia (about) in 90
days
or nights during a year. Only 22 degree halo is more common than parhelia
and
22 degree tangent arcs which are about equally common.
Parhelia usually shows some colors and some times those colors are really
vivid. Only very faint parhelia can be virtually colorless. Usually only
red
and yellow colors can be easily seen but very often at least green and
blue is
visible too (expecially when you are wearing sun glasses).
Parhelia can have several different appearances: 1) a colored spot which
can be
more or less like a vertical column or a triangle, 2) case 1 with a
horisontal
tail outward, 3) brightening or broader section on the side of 22 degree
halo
and 4) "a bright, usually colored, cloud". Which one of those four cases
are
rarest? Cases 1 and 3 are very usual. Cases 2 and 4 are not so usual but I
won't say that they are rare...
Good books about halos are Robert Greenler's: "Rainbows, Halos and
Glories"
(Cambridge University Press, New York, 1980) and Walter Tape's
"Atmoshperic
Halos" (American Geophysical Union, Washington D.C., 1994). If you are
interested about halos, please, read at least later one which is the best
halo
book ever written in English...
Regards,
Jarmo Moilanen
Leader of FHON (the Finnish Halo Observing Network)
|=============================================
| Jarmo Moilanen
| Vuolijoentie 2096
| 91760 Säräisniemi
| FINLAND
| e-mail: jarmom_at_netppl.fi
| homepage: http://www.netppl.fi/~jarmom/index.htm
|=============================================
| Chuck,
|
| I am surprised that this form of the sun-dag is the most rare to
| you. Here (Aarhus, DK) it is by far the most common of all the
| arc phenomena. In fact I have yet to see an uncolored sundog!
|
| I catched a photo of one a month back or so, but my scanner is
| not quite up yet... Will let you know when and where I post the
| picture.
|
| Thomas Dall
| Aarhus, Denmark
|
| On Mon, 27 Dec 1999, Chuck O'Connell wrote:
|
| > Hi Bev,
| >
| > Sundogs can give a couple of different appearances.
| >
| > The second appearance occurs when the 'sun dog' is formed on a
| > cloud that is much closer to the observer. In this case the 'rainbow'
is
| > spread out 'across' the cloud. Because of this the normal uniform
| > thickness
| > of the color bands becomes distorted - some seem longer and smeared
out.
| > Some people refer to this as a 'rainbow cloud'. I've only observed
this a
| > handful
| > of times in 20 years of looking. It is very beautiful. I've also
never
|