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>> Moon Dog is above the line between the Moon and Dogs. Many --Boundary_(ID_pEM7Blefh3HtFC+s4NyCwg) Content-type: text/plain; charset=windows-1252 Content-transfer-encoding: quoted-printable 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. The dogs are formed where the = prisms are preferentially aligned (presumably as they = fall).</div><div>See: <a = href=3D"http://en.wikipedia.org/wiki/Sun_dog">http://en.wikipedia.org/wiki= /Sun_dog</a></div><div>Also: <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: <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. (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. 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 & Alison Webster wrote:</div><br = class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><div>Hi = Paul & All, = July = 28, 2010<br> 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> = 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> 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> 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> 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> 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> 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> = 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> 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> 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" <<a = href=3D"mailto:psboyer@eastlink.ca">psboyer@eastlink.ca</a>><br>To: = <<a = href=3D"mailto:naturens@chebucto.ns.ca">naturens@chebucto.ns.ca</a>><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. 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).<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. 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. 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. 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.<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. 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. 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.<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. = 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.<br></blockquote><blockquote = type=3D"cite"><br></blockquote><blockquote type=3D"cite">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<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. 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. 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 -- = 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?<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 & Alison Webster <<a = href=3D"mailto:dwebster@glinx.com">dwebster@glinx.com</a>>:<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, = &n= bsp; July 25, = 2010<br></blockquote></blockquote></blockquote></blockquote><blockquote = type=3D"cite"><blockquote type=3D"cite"><blockquote = type=3D"cite"><blockquote type=3D"cite"> 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 & 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 & All, = &n= bsp; July 25, = 2010<br></blockquote></blockquote></blockquote></blockquote><blockquote = type=3D"cite"><blockquote type=3D"cite"><blockquote = type=3D"cite"><blockquote type=3D"cite"> 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"> 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"> 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"> 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. = 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. Then = combine the picture using HR (high dynamic range) software. [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. 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"> 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"> <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"> Ian = McKay<br></blockquote></blockquote></blockquote></blockquote><blockquote = type=3D"cite"><blockquote type=3D"cite"><blockquote = type=3D"cite"><blockquote type=3D"cite"> 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"> 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"> 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"> = 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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