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Hi Again, July 25, 2010
For some reason this has not been posted yet so will try again with =
cc. DW
----- Original Message -----=20
From: David & Alison Webster=20
To: naturens@chebucto.ns.ca=20
Sent: Sunday, July 25, 2010 9:53 AM
Subject: Re: [NatureNS] Pic of Moondogs over Scots Bay
Hi Paul & All, July 25, 2010
Why the dogs are slightly above moon center is an interesting =
question. I will take a qualitative stab at attempting to rationalize =
this and perhaps someone versed in optics and spherical geometry can =
generate numbers.
The dogs lie on and are, in effect, unusually bright areas in a 22o =
halo around the moon. One may consequently conclude that the dogs arise =
by convergence of refraction from numerous points.=20
If one assumes that the Cirrus clouds containing the ice crystals =
line in a plane that by projection would form a concentric spherical =
shell and with the light source (sun or moon) at a suitably low angle, =
this shell of ice crystals will act as a lens in the sense that numerous =
points in a localized zone of this curved shell will lie at 22o between =
the observer and the moon.=20
This convergence of refracted rays will be greatest where =
substantial light is refracted from the curved shell that lies above the =
moon/observer path, thus leading to a dog slightly above this level.
Yt, Dave Webster, Kentville
----- Original Message -----=20
From: Paul S. Boyer=20
To: naturens@chebucto.ns.ca=20
Sent: Saturday, July 24, 2010 7:23 PM
Subject: Re: [NatureNS] Pic of Moondogs over Scots Bay
Congratulations, Ian. This is a very interesting shot.=20
I think that next time you could try a quick sequence of shot at =
different exposures. Then combine the picture using HR (high dynamic =
range) software. [See: =
http://en.wikipedia.org/wiki/High_dynamic_range_imaging]
I was puzzled to note that the two =93dogs=94 do not lie in a straight =
line with the moon. I can't explain that, but is is the same a the =
configuration shown in the Wikipedia article on moon dogs =
[http://en.wikipedia.org/Moon_dog].
=97Paul
On Jul 24, 2010, at 6:42 PM, Ian McKay wrote:
I managed to capture something I had only seen once before - =
Moondogs. Much like Sundogs but caused by the light of the moon. The =
corona was huge. I had to use a pretty big aperture to catch a little of =
what my eye was seeing. Not great but it comes close.
http://www.amimckay.com/graphics/moondogs-scotsbay.jpg
Ian McKay
Scots Bay=20
No virus found in this outgoing message.
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Version: 9.0.851 / Virus Database: 271.1.1/3025 - Release Date: =
07/24/10 03:36:00
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No virus found in this incoming message.
Checked by AVG - www.avg.com=20
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--Boundary_(ID_yuOi2oGbt+XNIImvKjOPWw)
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style=3D"WORD-WRAP: break-word; -webkit-nbsp-mode: space; =
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<DIV><FONT size=3D2>Hi Again, =20
July 25, 2010</FONT></DIV>
<DIV><FONT size=3D2> For some reason this has not been =
posted=20
yet so will try again with cc. DW</FONT></DIV>
<DIV style=3D"FONT: 10pt arial">----- Original Message -----=20
<DIV style=3D"BACKGROUND: #e4e4e4; font-color: black"><B>From:</B> <A=20
title=3Ddwebster@glinx.com href=3D"mailto:dwebster@glinx.com">David =
& Alison=20
Webster</A> </DIV>
<DIV><B>To:</B> <A title=3Dnaturens@chebucto.ns.ca=20
href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</A> =
</DIV>
<DIV><B>Sent:</B> Sunday, July 25, 2010 9:53 AM</DIV>
<DIV><B>Subject:</B> Re: [NatureNS] Pic of Moondogs over Scots =
Bay</DIV></DIV>
<DIV><BR></DIV>
<DIV><FONT size=3D2>Hi Paul & All, =
=20
July 25, 2010</FONT></DIV>
<DIV><FONT size=3D2> Why the dogs are slightly above =
moon center=20
is an interesting question. I will take a qualitative stab =
at attempting to=20
rationalize this and perhaps someone versed in optics and spherical =
geometry can generate numbers.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2> The dogs lie on and are, in =
effect,=20
unusually bright areas in a 22o halo around the moon. One may =
consequently=20
conclude that the dogs arise by convergence of refraction =
from numerous=20
points. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT size=3D2> If one assumes that the Cirrus =
clouds=20
containing the ice crystals line in a plane that by projection =
would form a=20
concentric spherical shell and with the light source (sun or =
moon) at=20
a suitably low angle, this shell of ice crystals will act as a lens in =
the sense=20
that numerous points in a localized zone of this curved shell will =
lie at=20
22o between the observer and the moon. </FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2> This convergence of refracted =
rays will be=20
greatest where substantial light is refracted from the curved shell that =
lies=20
above the moon/observer path, thus leading to a dog slightly above this=20
level.</FONT></DIV>
<DIV><FONT size=3D2></FONT> </DIV>
<DIV><FONT size=3D2>Yt, Dave Webster, Kentville</FONT></DIV>
<BLOCKQUOTE=20
style=3D"BORDER-LEFT: #000000 2px solid; PADDING-LEFT: 5px; =
PADDING-RIGHT: 0px; MARGIN-LEFT: 5px; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"FONT: 10pt arial; BACKGROUND: #e4e4e4; font-color: =
black"><B>From:</B>=20
<A title=3Dpsboyer@eastlink.ca =
href=3D"mailto:psboyer@eastlink.ca">Paul S.=20
Bo