[NatureNS] Pic of Moondogs over Scots Bay

From: "Paul S. Boyer" <psboyer@eastlink.ca>
Date: Wed, 28 Jul 2010 14:52:53 -0300
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Index of Subjects

&gt;&gt; Moon Dog is above the line between the Moon and Dogs. Many 

--Boundary_(ID_pEM7Blefh3HtFC+s4NyCwg)
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Hello atmospheric dog-enthusiasts!

I finally have checked Wikipedia, and have not found the explanation for =
any difference between the sun-dogs and the moon-dogs, even though that =
is what we seem to be seeing.

I did find that the great Wikipedia says that the refraction we are =
seeing in the common 22=B0 halo is from randomly scattered ice prisms.  =
The dogs are formed where the prisms are preferentially aligned =
(presumably as they fall).
See: http://en.wikipedia.org/wiki/Sun_dog
Also: http://en.wikipedia.org/wiki/22=B0_halo

There is also a nice diagram at: =
http://www.atoptics.co.uk/halo/dogfm.htm
The illustration shows flat prisms floating most commonly with the =
c-axis vertical, but this is also the shortest physical dimension, so =
they are not dropping like bombs, as I had pictured them.  (I think that =
that is a different case.)

I wonder if the non-colinear appearance of the dogs and the moon could =
be merely a distortion of a rather wide-angle lens.  This is suggested =
by the picture at:
http://www.atoptics.co.uk/halo/parmoon.htm
where the landscape is obviously distorted.

=97 Paul


On Jul 28, 2010, at 1:48 PM, David & Alison Webster wrote:

> Hi Paul & All,            July 28, 2010
>   I still have more questions than answers and even the idea that the =
altitude of moon dogs is usually greater than moon altitude remains =
conjectural; something to watch for.
>=20
>   However, the angle 22o keeps coming up so any concept of halo or dog =
generation must be consistent with an angle of reflection/refraction of =
22o. This seems to make at least qualitative sense if flat crystals are =
assumed; i.e. two flat parallel surfaces (assuming reflection increases =
as the angle of incidence increases).
> PLATES
>   With a plate-like ice crystal [index of refraction 1.31] vertical, =
about parallel to the eye-moon axis and 22o from this axis, the angle of =
incidence would be 68o (implying substantial reflection) and the angle =
of refraction would be 45o (implying substantial and perhaps repetitive =
internal reflection) with about half of the light that entered the =
crystal exiting at 22o to supplement the reflected light.
>=20
>   At angles greater than 22o from the axis there would be less =
reflection from the air/ice interface and an angle of refraction of less =
than 45o leading to less internal reflection (i.e. more escape of light =
away from the observer).
>=20
>   At angles less than 22o from the axis, more of the incident light =
would be reflected but area of crystal intercepted by light will =
decrease as
>   sin(90-angle of incidence)
> and e.g. moving in from 22o to 15o will decrease intercepted crystal =
area from 0.37 to 0.25. And the angle of reflection would exceed 45o =
leading to more internal reflection and less escape of light from the =
crystal.
>=20
> RODS
>   With rods, presumably hexagonal in cross-section, I can't see how =
22o fits unless a crystal alignment parallel to the eye-moon axis is =
assumed as well as a hexagonal face normal to the moon-crystal-eye =
plane.
>=20
>   On the macro scale I think the following framework should be valid. =
With the 22o angle represented by a cone at the observer's eye with apex =
of 44o and axis pointing at the moon, the zone of additional light will =
be somewhere along the intersection of a hemispheric shell and the cone =
(the observer is in the middle of a flat disk and under the hemisphere).
>=20
>   This zone of intersection will be a nearly circular halo when the =
moon is relatively high in the sky and a roughly football-shaped when =
low [i.e. truncated on the lower side and squashed down on top].
>=20
>   On an unrelated matter, in the days before weather forecasts, the =
number of stars inside of this 'ring-around-the-moon' was used to =
estimate the number of days before a storm... no stars; storm soon, 3 =
stars; storm in 3 days etc.
>=20
> Yt, Dave Webster, Kentville
>=20
>=20
> ----- Original Message ----- From: "Paul S. Boyer" =
<psboyer@eastlink.ca>
> To: <naturens@chebucto.ns.ca>
> Sent: Tuesday, July 27, 2010 9:49 AM
> Subject: Re: [NatureNS] Pic of Moondogs over Scots Bay
>=20
>=20
>> I don't think that the difference in temperature (day to night) is an =
important factor here, because the temperature where the proper form of =
ice crystal occurs would be the same in any case, in order to get the =
crystals of the proper form.  The crystals responsible (and most =
effective) for many of these phenomena are elongate prisms,  They are =
small (but up to a mm long) rod-like things, and so they fall very =
slowly because they are small and not as dense as a raindrop because of =
air inclusions. As they fall, the prisms line up (at least =
statistically) in a roughly vertical position, like bombs falling out of =
an airplane (if you think of the old WWII documentaries).
>>=20
>> Critical must be the orientation of the crystals relative to the =
plane defined by the light source (sun or moon), the spot in the sky you =
are viewing, and your eye.  The best, strongest effect would then be =
when these little prisms would be aligned perpendicular to that plane.
>>=20
>> Ordinarily, one would expect the dogs to form off to the sides of the =
light source (sun or moon) because the prisms are falling down toward =
the center of the Earth, and therefore works best for a plane =
perpendicular to the downward-direction.  This is, indeed, what we would =
expect to see if looking parallel to the plane containing all those =
little refracting ice-crystals, aligned vertically as they fall.
>>=20
>> It is possible that patchiness of the clouds contributes to this, but =
I rather doubt it.  For one thing, these crystals usually form in =
cirrostratus clouds, which form a more or less continuous veil, under =
the conditions that give us the circle (or circles) around the moon.  =
There is no strong convection in such circumstances, and thus little =
patchiness.
>>=20
>> On the Internet I find all the solar dogs are in line with the sun, =
yet the few moon-dog pictures show a displacement of one or both of the =
dogs above the angular elevation of the moon.  So, I am still puzzled, =
and I don't know the answer definitively.
>>=20
>> As an hypothesis, I might suggest that we are dealing with a matter =
of perspective here.  Almost all the sun-dog pictures I have seen have =
the sun quite low to the horizon;   therefore, we are in such cases =
looking at the layer containing the ice crystals almost edge-on.
>>=20
>> The reason we seldom see sun-dogs high in the sky, is probably that =
the sun is just too bright then.
>>=20
>> The moon dogs, however, show up nicely even when the moon is higher =
in the sky.  Assuming that the layer with the ice crystal prisms is =
horizontal (or, more accurately, shell-like around a segment of the =
earth =97 though this difference may not be important), then we have a =
more complex geometry.  The crystals are much closer to us than the =
light source, which can be considered at infinity in this case.  We are =
looking slighting upward and obliquely at the underside of the =
refracting layer.  So it may be that the crystals most effectively =
refracting the light from the moon are those which appear, by =
perspective to us, somewhat higher in angular elevation that the =
illuminating body.
>>=20
>> So, my tentative guess is that this is matter of perspective.  A =
simple experiment with a lightbulb and an optical prism might in this =
case be very =93illuminating.=94
>>=20
>>=20
>> On Jul 26, 2010, at 9:06 AM, Larry Bogan wrote:
>>=20
>>> The misalignment of the Moon Dogs is due to the non-uniformity of =
the cloud cover.
>>>=20
>>> The Sun/Moon Dogs are created by the ice crystals in the clouds and =
are usually arcs of some length (up and down). In most cases the clouds =
are not uniform and they aren't in this photo.  It just so happens that =
on the right side there is no clouds on the lower part so it looks as if =
the Moon Dog is above the line between the Moon and Dogs. Many times =
there is only a Dog on one side if the clouds are very spotty and the =
misalignment can not be determined.
>>>=20
>>> Larry Bogan
>>>=20
>>> Steve Shaw wrote:
>>>> Interestingly, the one image of the same thing in Wikipedia (search =
for 'Moon dogs') shows the same discrepancy, with the two dogs each =
elevated by perhaps 10-15 degrees above an imaginary horizontal line =
drawn through the moon. The short associated text there indicates that =
the explanation for Moon Dogs is exactly analogous to that for Sun Dogs =
(refracting ice crystals 22 degrees out), but this view has to be =
suspect.
>>>>=20
>>>> The longer article on Sun Dogs stresses that these always lie in =
the same horizontal plane as the sun.  The ice crystals supposedly =
sometimes sink placidly and line up vertically in the atmosphere, =
whereupon two sun dogs may appear.
>>>>=20
>>>> As the line-up in the two optical phenomena is somewhat different, =
suggesting a common explanation for both can't be exactly correct --  =
we're missing something.  Perhaps the form of the ice crystals differs =
when these are formed in sunlight (warmer) than when it is colder up =
there, at night in moonlight?
>>>> Steve
>>>>=20
>>>>=20
>>>> Quoting David & Alison Webster <dwebster@glinx.com>:
>>>>=20
>>>>> Hi Again,                July 25, 2010
>>>>>   For some reason this has not been posted yet so will try again =
with cc. DW
>>>>> ----- Original Message -----
>>>>> From: David & Alison Webster
>>>>> To: naturens@chebucto.ns.ca
>>>>> Sent: Sunday, July 25, 2010 9:53 AM
>>>>> Subject: Re: [NatureNS] Pic of Moondogs over Scots Bay
>>>>>=20
>>>>>=20
>>>>> 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.
>>>>>=20
>>>>>   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.
>>>>>=20
>>>>> Yt, Dave Webster, Kentville
>>>>> ----- Original Message -----
>>>>> From: Paul S. Boyer
>>>>> To: naturens@chebucto.ns.ca
>>>>> Sent: Saturday, July 24, 2010 7:23 PM
>>>>> Subject: Re: [NatureNS] Pic of Moondogs over Scots Bay
>>>>>=20
>>>>>=20
>>>>> Congratulations, Ian.  This is a very interesting shot.
>>>>>=20
>>>>>=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]
>>>>>=20
>>>>>=20
>>>>> 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].
>>>>>=20
>>>>>=20
>>>>> =97Paul
>>>>>=20
>>>>>=20
>>>>> On Jul 24, 2010, at 6:42 PM, Ian McKay wrote:
>>>>>=20
>>>>>=20
>>>>>   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
>>>>>=20
>>>>>   Ian McKay
>>>>>   Scots Bay
>>>>>=20
>>>>>   No virus found in this outgoing message.
>>>>>   Checked by AVG - www.avg.com
>>>>>   Version: 9.0.851 / Virus Database: 271.1.1/3025 - Release Date: =
07/24/10 03:36:00
>>>>>=20
>>>>=20
>>>>=20
>>>=20
>=20
>=20
> =
--------------------------------------------------------------------------=
------
>=20
>=20
>=20
> No virus found in this incoming message.
> Checked by AVG - www.avg.com
> Version: 9.0.851 / Virus Database: 271.1.1/3028 - Release Date: =
07/25/10 15:36:00
>=20


--Boundary_(ID_pEM7Blefh3HtFC+s4NyCwg)
Content-type: text/html; charset=windows-1252
Content-transfer-encoding: quoted-printable

<html><head></head><body style=3D"word-wrap: break-word; =
-webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">Hello =
atmospheric dog-enthusiasts!<div><br></div><div>I finally have checked =
Wikipedia, and have not found the explanation for any difference between =
the sun-dogs and the moon-dogs, even though that is what we seem to be =
seeing.</div><div><br></div><div>I did find that the great Wikipedia =
says that the refraction we are seeing in the common 22=B0 halo is from =
randomly scattered ice prisms. &nbsp;The dogs are formed where the =
prisms are preferentially aligned (presumably as they =
fall).</div><div>See:&nbsp;<a =
href=3D"http://en.wikipedia.org/wiki/Sun_dog">http://en.wikipedia.org/wiki=
/Sun_dog</a></div><div>Also:&nbsp;<a =
href=3D"http://en.wikipedia.org/wiki/22=B0_halo">http://en.wikipedia.org/w=
iki/22=B0_halo</a></div><div><br></div><div>There is also a nice diagram =
at:&nbsp;<a =
href=3D"http://www.atoptics.co.uk/halo/dogfm.htm">http://www.atoptics.co.u=
k/halo/dogfm.htm</a></div><div>The illustration shows flat prisms =
floating most commonly with the c-axis vertical, but this is also the =
<i>shortest physical</i> dimension, so they are not dropping like bombs, =
as I had pictured them. &nbsp;(I think that that is a different =
case.)</div><div><br></div><div>I wonder if the non-colinear appearance =
of the dogs and the moon could be merely a distortion of a rather =
wide-angle lens. &nbsp;This is suggested by the picture at:</div><div><a =
href=3D"http://www.atoptics.co.uk/halo/parmoon.htm">http://www.atoptics.co=
.uk/halo/parmoon.htm</a></div><div>where the landscape is obviously =
distorted.</div><div><br></div><div>=97 =
Paul</div><div><br></div><div><br><div><div>On Jul 28, 2010, at 1:48 PM, =
David &amp; Alison Webster wrote:</div><br =
class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div>Hi =
Paul &amp; All, =
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;July =
28, 2010<br> &nbsp;&nbsp;I still have more questions than answers and =
even the idea that the altitude of moon dogs is usually greater than =
moon altitude remains conjectural; something to watch for.<br><br> =
&nbsp;&nbsp;However, the angle 22o keeps coming up so any concept of =
halo or dog generation must be consistent with an angle of =
reflection/refraction of 22o. This seems to make at least qualitative =
sense if flat crystals are assumed; i.e. two flat parallel surfaces =
(assuming reflection increases as the angle of incidence =
increases).<br>PLATES<br> &nbsp;&nbsp;With a plate-like ice crystal =
[index of refraction 1.31] vertical, about parallel to the eye-moon axis =
and 22o from this axis, the angle of incidence would be 68o (implying =
substantial reflection) and the angle of refraction would be 45o =
(implying substantial and perhaps repetitive internal reflection) with =
about half of the light that entered the crystal exiting at 22o to =
supplement the reflected light.<br><br> &nbsp;&nbsp;At angles greater =
than 22o from the axis there would be less reflection from the air/ice =
interface and an angle of refraction of less than 45o leading to less =
internal reflection (i.e. more escape of light away from the =
observer).<br><br> &nbsp;&nbsp;At angles less than 22o from the axis, =
more of the incident light would be reflected but area of crystal =
intercepted by light will decrease as<br> &nbsp;&nbsp;sin(90-angle of =
incidence)<br>and e.g. moving in from 22o to 15o will decrease =
intercepted crystal area from 0.37 to 0.25. And the angle of reflection =
would exceed 45o leading to more internal reflection and less escape of =
light from the crystal.<br><br>RODS<br> &nbsp;&nbsp;With rods, =
presumably hexagonal in cross-section, I can't see how 22o fits unless a =
crystal alignment parallel to the eye-moon axis is assumed as well as a =
hexagonal face normal to the moon-crystal-eye plane.<br><br> =
&nbsp;&nbsp;On the macro scale I think the following framework should be =
valid. With the 22o angle represented by a cone at the observer's eye =
with apex of 44o and axis pointing at the moon, the zone of additional =
light will be somewhere along the intersection of a hemispheric shell =
and the cone (the observer is in the middle of a flat disk and under the =
hemisphere).<br><br> &nbsp;&nbsp;This zone of intersection will be a =
nearly circular halo when the moon is relatively high in the sky and a =
roughly football-shaped when low [i.e. truncated on the lower side and =
squashed down on top].<br><br> &nbsp;&nbsp;On an unrelated matter, in =
the days before weather forecasts, the number of stars inside of this =
'ring-around-the-moon' was used to estimate the number of days before a =
storm... no stars; storm soon, 3 stars; storm in 3 days etc.<br><br>Yt, =
Dave Webster, Kentville<br><br><br>----- Original Message ----- From: =
"Paul S. Boyer" &lt;<a =
href=3D"mailto:psboyer@eastlink.ca">psboyer@eastlink.ca</a>&gt;<br>To: =
&lt;<a =
href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</a>&gt;<br=
>Sent: Tuesday, July 27, 2010 9:49 AM<br>Subject: Re: [NatureNS] Pic of =
Moondogs over Scots Bay<br><br><br><blockquote type=3D"cite">I don't =
think that the difference in temperature (day to night) is an important =
factor here, because the temperature where the proper form of ice =
crystal occurs would be the same in any case, in order to get the =
crystals of the proper form. &nbsp;The crystals responsible (and most =
effective) for many of these phenomena are elongate prisms, &nbsp;They =
are small (but up to a mm long) rod-like things, and so they fall very =
slowly because they are small and not as dense as a raindrop because of =
air inclusions. As they fall, the prisms line up (at least =
statistically) in a roughly vertical position, like bombs falling out of =
an airplane (if you think of the old WWII =
documentaries).<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">Critical must =
be the orientation of the crystals relative to the plane defined by the =
light source (sun or moon), the spot in the sky you are viewing, and =
your eye. &nbsp;The best, strongest effect would then be when these =
little prisms would be aligned perpendicular to that =
plane.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">Ordinarily, one =
would expect the dogs to form off to the sides of the light source (sun =
or moon) because the prisms are falling down toward the center of the =
Earth, and therefore works best for a plane perpendicular to the =
downward-direction. &nbsp;This is, indeed, what we would expect to see =
if looking parallel to the plane containing all those little refracting =
ice-crystals, aligned vertically as they =
fall.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">It is possible =
that patchiness of the clouds contributes to this, but I rather doubt =
it. &nbsp;For one thing, these crystals usually form in cirrostratus =
clouds, which form a more or less continuous veil, under the conditions =
that give us the circle (or circles) around the moon. &nbsp;There is no =
strong convection in such circumstances, and thus little =
patchiness.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">On the Internet =
I find all the solar dogs are in line with the sun, yet the few moon-dog =
pictures show a displacement of one or both of the dogs above the =
angular elevation of the moon. &nbsp;So, I am still puzzled, and I don't =
know the answer definitively.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">As an =
hypothesis, I might suggest that we are dealing with a matter of =
perspective here. &nbsp;Almost all the sun-dog pictures I have seen have =
the sun quite low to the horizon; &nbsp;&nbsp;therefore, we are in such =
cases looking at the layer containing the ice crystals almost =
edge-on.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">The reason we =
seldom see sun-dogs high in the sky, is probably that the sun is just =
too bright then.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">The moon dogs, =
however, show up nicely even when the moon is higher in the sky. =
&nbsp;Assuming that the layer with the ice crystal prisms is horizontal =
(or, more accurately, shell-like around a segment of the earth =97 =
though this difference may not be important), then we have a more =
complex geometry. &nbsp;The crystals are much closer to us than the =
light source, which can be considered at infinity in this case. &nbsp;We =
are looking slighting upward and obliquely at the underside of the =
refracting layer. &nbsp;So it may be that the crystals most effectively =
refracting the light from the moon are those which appear, by =
perspective to us, somewhat higher in angular elevation that the =
illuminating body.<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">So, my =
tentative guess is that this is matter of perspective. &nbsp;A simple =
experiment with a lightbulb and an optical prism might in this case be =
very =93illuminating.=94<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite">On Jul 26, =
2010, at 9:06 AM, Larry Bogan wrote:<br></blockquote><blockquote =
type=3D"cite"><br></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite">The misalignment of the Moon Dogs is due to the =
non-uniformity of the cloud =
cover.<br></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite">The Sun/Moon Dogs are created by =
the ice crystals in the clouds and are usually arcs of some length (up =
and down). In most cases the clouds are not uniform and they aren't in =
this photo. &nbsp;It just so happens that on the right side there is no =
clouds on the lower part so it looks as if the Moon Dog is above the =
line between the Moon and Dogs. Many times there is only a Dog on one =
side if the clouds are very spotty and the misalignment can not be =
determined.<br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite">Larry =
Bogan<br></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite">Steve Shaw =
wrote:<br></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Interestingly, the one image of =
the same thing in Wikipedia (search for 'Moon dogs') shows the same =
discrepancy, with the two dogs each elevated by perhaps 10-15 degrees =
above an imaginary horizontal line drawn through the moon. The short =
associated text there indicates that the explanation for Moon Dogs is =
exactly analogous to that for Sun Dogs (refracting ice crystals 22 =
degrees out), but this view has to be =
suspect.<br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote type=3D"cite">The =
longer article on Sun Dogs stresses that these always lie in the same =
horizontal plane as the sun. &nbsp;The ice crystals supposedly sometimes =
sink placidly and line up vertically in the atmosphere, whereupon two =
sun dogs may =
appear.<br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote type=3D"cite"> As =
the line-up in the two optical phenomena is somewhat different, =
suggesting a common explanation for both can't be exactly correct -- =
&nbsp;we're missing something. &nbsp;Perhaps the form of the ice =
crystals differs when these are formed in sunlight (warmer) than when it =
is colder up there, at night in =
moonlight?<br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite">Steve<br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote type=3D"cite">Quoting =
David &amp; Alison Webster &lt;<a =
href=3D"mailto:dwebster@glinx.com">dwebster@glinx.com</a>&gt;:<br></blockq=
uote></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Hi Again, =
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n=
bsp;&nbsp;&nbsp;July 25, =
2010<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;For some reason =
this has not been posted yet so will try again with cc. =
DW<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">----- Original Message =
-----<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">From: David &amp; Alison =
Webster<br></blockquote></blockquote></blockquote></blockquote><blockquote=
 type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">To: <a =
href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</a><br></b=
lockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Sent: Sunday, July 25, 2010 9:53 =
AM<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Subject: Re: [NatureNS] Pic of =
Moondogs over Scots =
Bay<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Hi Paul &amp; All, =
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&n=
bsp;&nbsp;&nbsp;July 25, =
2010<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;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.<br></blockquote></blockquote></blockquote></blockquote><blockquot=
e type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;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.<br></blockquote></blockquote></blockquote></blockquote><blockquote=
 type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;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.<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;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.<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite">Yt, Dave Webster, =
Kentville<br></blockquote></blockquote></blockquote></blockquote><blockquo=
te type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> ----- Original Message =
-----<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> From: Paul S. =
Boyer<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> To: <a =
href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</a><br></b=
lockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> Sent: Saturday, July 24, 2010 =
7:23 =
PM<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> Subject: Re: [NatureNS] Pic of =
Moondogs over Scots =
Bay<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> Congratulations, Ian. =
&nbsp;This is a very interesting =
shot.<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> I think that next time you =
could try a quick sequence of shot at different exposures. &nbsp;Then =
combine the picture using HR (high dynamic range) software. &nbsp;[See: =
<a =
href=3D"http://en.wikipedia.org/wiki/High_dynamic_range_imaging]">http://e=
n.wikipedia.org/wiki/High_dynamic_range_imaging]</a><br></blockquote></blo=
ckquote></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> I was puzzled to note that the =
two =93dogs=94 do not lie in a straight line with the moon. &nbsp;I =
can't explain that, but is is the same a the configuration shown in the =
Wikipedia article on moon dogs [<a =
href=3D"http://en.wikipedia.org/Moon_dog">http://en.wikipedia.org/Moon_dog=
</a>].<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> =
=97Paul<br></blockquote></blockquote></blockquote></blockquote><blockquote=
 type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> On Jul 24, 2010, at 6:42 PM, =
Ian McKay =
wrote:<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;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.<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;<a =
href=3D"http://www.amimckay.com/graphics/moondogs-scotsbay.jpg">http://www=
.amimckay.com/graphics/moondogs-scotsbay.jpg</a><br></blockquote></blockqu=
ote></blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;Ian =
McKay<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;Scots =
Bay<br></blockquote></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;No virus found in =
this outgoing =
message.<br></blockquote></blockquote></blockquote></blockquote><blockquot=
e type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"> &nbsp;&nbsp;Checked by AVG - <a =
href=3D"http://www.avg.com">www.avg.com</a><br></blockquote></blockquote><=
/blockquote></blockquote><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote type=3D"cite"> =
&nbsp;&nbsp;Version: 9.0.851 / Virus Database: 271.1.1/3025 - Release =
Date: 07/24/10 =
03:36:00<br></blockquote></blockquote></blockquote></blockquote><blockquot=
e type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote></blockquote><blo=
ckquote type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote></blockquote><blockquote =
type=3D"cite"><blockquote =
type=3D"cite"><br></blockquote></blockquote><br><br>----------------------=
----------------------------------------------------------<br><br><br><br>=
No virus found in this incoming message.<br>Checked by AVG - <a =
href=3D"http://www.avg.com">www.avg.com</a><br>Version: 9.0.851 / Virus =
Database: 271.1.1/3028 - Release Date: 07/25/10 =
15:36:00<br><br></div></blockquote></div><br></div></body></html>=

--Boundary_(ID_pEM7Blefh3HtFC+s4NyCwg)--

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