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APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 3:54 am
by APOD Robot
Serene Paraselene
Explanation: Nestled in the Austrian Alps, frozen
Lake Ossiach stretches across the foreground of this serene view. Recorded on March 1, the night sky includes a nearly full Moon and bright planet Saturn seen through thin clouds near picture center. It also includes a remarkably bright and colorful
moondog or paraselene at the left. Analogous to a
sundog or parhelion, the paraselene
is produced by moonlight shining through thin,
hexagonal-shaped ice crystals in high
cirrus clouds. As determined by the ice crystal geometry, the Moon is 22 degrees from the lovely paraselene.
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Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 8:38 am
by watcher
It looks like the moon is in the shape of a hexagon. It this just by chance because of the clouds? Or is because of the hexagonal ice crystals?
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 9:24 am
by 13 Rabbit
It looks like there is a moon dog at 22 1/2 degrees to the right also.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 11:20 am
by Joed
How did it get the name/why is it called. Moondog?
Serene Paraselene northa' Slovene
Posted: Fri Apr 02, 2010 1:32 pm
by neufer
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 1:36 pm
by biddie67
If the cloud cover were consistent all around the area of the moon, could a circle of reflected light be seen at that distance?
I've seen circles around the moon before but they were a lot closer than the 22 degrees described above - can the ice-crystals vary enough in their positions to cause the different positions of the moondogs or circles?
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 2:17 pm
by Amir
Joed wrote:How did it get the name/why is it called. Moondog?
maybe because those two bright spots look like two dogs walking with moon!
biddie67 wrote:I've seen circles around the moon before but they were a lot closer than the 22 degrees described above - can the ice-crystals vary enough in their positions to cause the different positions of the moondogs or circles?
are you talking about radius? closer that 22degrees in radius? cuz it's 22degrees in diameter i think!
of course there exists another 46 degree kind, but i haven't heard of any smaller.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 3:10 pm
by Chris Peterson
biddie67 wrote:If the cloud cover were consistent all around the area of the moon, could a circle of reflected light be seen at that distance?
I'm not sure what you're asking. If the clouds were more uniform, it is possible that the lunar halo and moondogs would be more uniform as well. But it depends not just on the uniformity of the clouds, but on their composition.
I've seen circles around the moon before but they were a lot closer than the 22 degrees described above - can the ice-crystals vary enough in their positions to cause the different positions of the moondogs or circles?
No. The 22° radius halo is the smallest true ring that can form around the Sun or Moon, and is the only possible radius for sundogs. Water droplets (or ice under the right conditions) can cause a broad glow around the Sun or Moon, a corona. This is always much smaller than a halo. It usually shows a faintly colored fringe that might make you think of a ring, although it is still quite different from a true halo. Perhaps this is what you saw, or perhaps you just misestimated the apparent size of a 22° halo on the sky.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 3:22 pm
by Chris Peterson
Joed wrote:How did it get the name/why is it called. Moondog?
Parhelion:
par(a) = beside,
helios = the Sun, thus beside the Sun. They
dog (follow) the Sun, so are
sundogs.
Paraselene:
para = beside,
selene = the Moon, thus beside the Moon. They
dog (follow) the Moon, so are
moondogs.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 02, 2010 3:38 pm
by biddie67
Thanks folks for trying to answer my questions - sorry they seemed rather fuzzy ....
Amir - I assumed the 22 degrees mentioned in the description referred to an angle of 22 degrees from a viewer's perspective on Earth between the moon and the moondog.
Chris - The rings that I was referring to were a lot less than 22 degrees - they must have been the coronas that you mentioned.
Thanks again .....
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Sun Apr 04, 2010 2:54 am
by lalunaquiza
i liked so much..
![Very Happy :D](./images/smilies/icon_biggrin.gif)
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Sun Apr 04, 2010 3:03 am
by lalunaquiza
watcher wrote:It looks like the moon is in the shape of a hexagon. It this just by chance because of the clouds? Or is because of the hexagonal ice crystals?
is because of the ice, these internships last very little, what would be almost imperseptivel, what caused this octogenarian we should focus on the clouds, could explain things more
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 09, 2010 5:43 am
by wetmoon
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 09, 2010 1:07 pm
by Chris Peterson
Except that
chemtrails are just paranoid fantasies.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 09, 2010 2:59 pm
by wonderboy
I don't see a moondog in this picture. Its not really that awe inspiring if I'm honest. One of my least favourite Apods.... sorry.
Re: APOD: Serene Paraselene (2010 Apr 02)
Posted: Fri Apr 09, 2010 3:19 pm
by bystander
wonderboy wrote:I don't see a moondog in this picture.
Left side of the picture, over the boat dock.