APOD: Serene Paraselene (2010 Apr 02)

APOD Robot · Post by **APOD Robot** » Fri Apr 02, 2010 3:54 am

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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watcher · Post by **watcher** » Fri Apr 02, 2010 8:38 am

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?

13 Rabbit · Post by **13 Rabbit** » Fri Apr 02, 2010 9:24 am

It looks like there is a moon dog at 22 1/2 degrees to the right also.

Joed · Post by **Joed** » Fri Apr 02, 2010 11:20 am

How did it get the name/why is it called. Moondog?

neufer · Post by **neufer** » Fri Apr 02, 2010 1:32 pm

http://en.wikipedia.org/wiki/Slovenia wrote:

Slovenian Coat of Arms

biddie67 · Post by **biddie67** » Fri Apr 02, 2010 1:36 pm

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?

Amir · Post by **Amir** » Fri Apr 02, 2010 2:17 pm

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.

Chris Peterson · Post by **Chris Peterson** » Fri Apr 02, 2010 3:10 pm

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.

Chris Peterson · Post by **Chris Peterson** » Fri Apr 02, 2010 3:22 pm

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.

biddie67 · Post by **biddie67** » Fri Apr 02, 2010 3:38 pm

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 .....

lalunaquiza · Post by **lalunaquiza** » Sun Apr 04, 2010 2:54 am

i liked so much..

lalunaquiza · Post by **lalunaquiza** » Sun Apr 04, 2010 3:03 am

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

wetmoon · Post by **wetmoon** » Fri Apr 09, 2010 5:43 am

These are chemtrail clouds: http://apod.nasa.gov/apod/ap100402.html

Chris Peterson · Post by **Chris Peterson** » Fri Apr 09, 2010 1:07 pm

wetmoon wrote:These are chemtrail clouds: http://apod.nasa.gov/apod/ap100402.html

Except that chemtrails are just paranoid fantasies.

wonderboy · Post by **wonderboy** » Fri Apr 09, 2010 2:59 pm

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.

bystander · Post by **bystander** » Fri Apr 09, 2010 3:19 pm

wonderboy wrote:I don't see a moondog in this picture.

Left side of the picture, over the boat dock.

Starship Asterisk*

APOD: Serene Paraselene (2010 Apr 02)

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Serene Paraselene northa' Slovene

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