APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Comments and questions about the APOD on the main view screen.

Have you ever seen a lunar halo?

Poll ended at Sun Dec 09, 2012 5:05 am

Yes
1344
88%
No
165
11%
What's a lunar halo?
27
2%
 
Total votes: 1536

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APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by APOD Robot » Mon Dec 03, 2012 5:05 am

Image A Quadruple Lunar Halo Over Spain

Explanation: Sometimes falling ice crystals make the atmosphere into a giant lens causing arcs and halos to appear around the Sun or Moon. This past Saturday night was just such a time near Madrid, Spain, where a winter sky displayed not only a bright Moon but as many as four rare lunar halos. The brightest object, near the top of the above image, is the Moon. Light from the Moon refracts through tumbling hexagonal ice crystals into a 22 degree halo seen surrounding the Moon. Elongating the 22 degree arc horizontally is a circumscribed halo caused by column ice crystals. More rare, some moonlight refracts through more distant tumbling ice crystals to form a (third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape. Furthermore, part of a whole 46 degree circular halo is also visible, so that an extremely rare -- especially for the Moon -- quadruple halo was actually imaged. The snow-capped trees in the foreground line the road Puerto de Navacerrada in the Sierra de Guadarrama mountain range near Madrid. Far in the background is a famous winter skyscape that includes Sirius, the belt of Orion, and Betelgeuse all visible between the inner and outer arcs. Halos and arcs typically last for minutes to hours, so if you do see one there should be time to invite family, friends or neighbors to share your unusual lensed vista of the sky.

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Case » Mon Dec 03, 2012 5:39 am

APOD wrote:Far in the background is a famous winter skyscape that includes Sirius, the belt of Orion, and Betelgeuse all visible between the inner and outer arcs.
Hey, bright Jupiter deserves a mention, too! Maybe not part of the “famous winter skyscape”, but it is the second brightest spot in the sky in this image.

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Ann » Mon Dec 03, 2012 6:03 am

What a beautiful APOD!

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Scott » Mon Dec 03, 2012 10:05 am

So, according to the professional astronomers at APOD, Dec 3 is now winter, and no longer autumn. When did this change take place?

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Boomer12k » Mon Dec 03, 2012 10:08 am

We had a similar thing, but it was through some fast moving clouds. This was last Wednesday Night. I saw the Moon behind the clouds, and they were not too thick to block out the Moon. There was a circle of brighter light around the Moon, and very similar to a halo. I have seen full halos here in Oregon in the past.

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Dario » Mon Dec 03, 2012 10:29 am

I have seen multiple halos a few times, but only once I caught a parlunic(?) circle. Sorry about the quality, the photo was taken in the early nineties and I couldn't see the second halo in the camera's viewfinder.
Image

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by RedFishBlueFish » Mon Dec 03, 2012 11:26 am

What is the bright blue spot in Orion, just outside the inner halo at about 5 o'clock: UFO, Healing Brush gone wrong, or some sort of reflection within the lens?

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Indigo_Sunrise » Mon Dec 03, 2012 11:48 am

From this link:
quadruple halo

Can someone please explain the difference between the '46* halo' and the 'infralateral arc'?
In that image, they look like they are part of the same halo/arc.... :?

TIA!

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by takaya » Mon Dec 03, 2012 11:56 am

Scott wrote:So, according to the professional astronomers at APOD, Dec 3 is now winter, and no longer autumn. When did this change take place?
According to the meteorologists, winter begins at Dec 1st. And so live the birds...

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by JohnD » Mon Dec 03, 2012 12:27 pm

Four rainbows?

I can see a complete circle around the Moon, and an arc between it and the horizon.
Where are the other two?

John

alireza mohammadi

Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by alireza mohammadi » Mon Dec 03, 2012 12:55 pm

با سلام
من تا به حال این پدیده را ندیده ام . منطقه ای که در آن رصد می کنم در منطقه ای خشک قرار دارد که کم تر می شود همچین پدیده ای رخ دهد.
ولی شاید تا به حال رخ داده باشد و من مشاهده نکرده باشم.

آسمانتان پر ستاره

Hi
I had not seen this phenomenon. An area in which I observed in a dry area, which is more or less the same phenomenon occurs.
But it had happened and I have not seen.

Starry Smant

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by owlice » Mon Dec 03, 2012 2:07 pm

JohnD wrote:Four rainbows?

I can see a complete circle around the Moon, and an arc between it and the horizon.
Where are the other two?

John
Four halos, not rainbows. Please see this image, to which the text links, for a labelled version.
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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by rstevenson » Mon Dec 03, 2012 2:29 pm

Scott wrote:So, according to the professional astronomers at APOD, Dec 3 is now winter, and no longer autumn. When did this change take place?
Winter occurs when it occurs -- locally, and in spite of definitions. A few decades ago I was working in northern Manitoba. That year the first snowfall occurred Sept. 3rd, and the last of that winter's snowfalls came May 27th. I was very grumpy that year.
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A Double Lunar Halo Over Spain

Post by geoffrey.landis » Mon Dec 03, 2012 3:00 pm

JohnD wrote:
Where are the other two?
I'll have to agree here-- I see a double halo, but if there are four halos in the image, I sure can't see them.

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Chris Peterson » Mon Dec 03, 2012 3:09 pm

Scott wrote:So, according to the professional astronomers at APOD, Dec 3 is now winter, and no longer autumn. When did this change take place?
All dates defining the beginning of seasons are arbitrary. Different dates are used by climatologists, astronomers, outdoorsmen, and civil authorities.

Regardless of any date commonly used, most people living at temperate latitudes, standing outside on a snowy night in early December, are probably going to be thinking "winter"!
Chris

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Chris Peterson » Mon Dec 03, 2012 3:16 pm

Indigo_Sunrise wrote:Can someone please explain the difference between the '46* halo' and the 'infralateral arc'?
In that image, they look like they are part of the same halo/arc.... :?
The two are formed by different mechanisms. By all accounts, they can be difficult to distinguish from each other, and are easily confused. There's some good information here.
Chris

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sfargo

Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by sfargo » Mon Dec 03, 2012 3:18 pm

RedFishBlueFish wrote:What is the bright blue spot in Orion, just outside the inner halo at about 5 o'clock: UFO, Healing Brush gone wrong, or some sort of reflection within the lens?
It look like a perfect circle. very unusual.

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Chris Peterson » Mon Dec 03, 2012 3:24 pm

RedFishBlueFish wrote:What is the bright blue spot in Orion, just outside the inner halo at about 5 o'clock: UFO, Healing Brush gone wrong, or some sort of reflection within the lens?
It appears to be an internal reflection. I see a subtle hexagonal structure aligned with the lunar diffraction spikes, created by the 6-leaf iris in this lens.
Chris

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zenfro

Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by zenfro » Mon Dec 03, 2012 4:37 pm

Dario wrote:I have seen multiple halos a few times, but only once I caught a parlunic(?) circle. Sorry about the quality, the photo was taken in the early nineties and I couldn't see the second halo in the camera's viewfinder.
Image
Fascinating. I have seen this kind of offset halo only once. I think it was caused by the moonlight reflecting off of a snowy landscape back into the ice crystals in the sky at a slightly different angle. The moon itself appeared to sit on the rim of the halo, just like in your picture. I also witnessed some jet contrails cutting through both halos in straight lines, almost as though someone were doing Euclidean geometry exercises in the sky!

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by JohnD » Mon Dec 03, 2012 4:55 pm

owlice wrote:
JohnD wrote:Four rainbows?

I can see a complete circle around the Moon, and an arc between it and the horizon.
Where are the other two?

John
Four halos, not rainbows. Please see this image, to which the text links, for a labelled version.

Thnaks, Owlice, but unconvincing.

The inner halo (apologies) is labelled both 22degrees and Circumscribed, and the outer arc the 46 degree halo and the infralateral arc.
That is astronomical legerdemain!
Nothing up my sleeves! Look! Abracadabra! Two haloes become ......... Four haloes!


But re-reading the original description, I note "Elongating the 22 degree arc horizontally is a circumscribed halo" Is this the tangential array touching the 22 halo at approx four oclock, and spreading outwards? I took that for very high cloud. Which I suppose it is, but as such unremarkable.
And the "(third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape" is paired with "part of a whole 46 degree circular halo is also visible" as the fourth halo. Two for the price of one - a bargain!

I'm glad to accept if you say so, that the tangential cloud is the second halo. A straight, not round halo, but anyway.

And that two different sorts of ice crystals can cause different effects, with the same "distant tumbling ice crystals" cause the third and fourth haloes? In the same relationship around the Moon, so it's difficult to accept that this is more than one phenomenon, a total of three haloes. Remarkable enough by themselves, but please explain further why four - I'll be most grateful.

John

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by florid_snow » Mon Dec 03, 2012 5:12 pm

You're right, it's not really well described compared to Atmospheric Optics POD (understandable, it is that site's focus) and I think there's only really good evidence for 3 halos here based on what I've read there. For the 22 degree halo, the two "different" halos are basically the colored one and the white one just outside it. It's hard to see many colors in the image but you can see some red light being separated in the image. That's a different type of ice crystal process than what is making the white blurred halo, probably two different layers of clouds.

Then the 46 degree halo, more often called the circum-horizontal arc (surprised that name wasn't mentioned here), is hard to split into two. I think basically they are claiming that because the halo is brighter towards the bottom of the image it must be the super-position of the regular 46 degree halo and one of its arcs? But it could just be brighter there because we are looking through a better organized part of the ice cloud. I would appreciate corrections and more theory from those more in the know, and recommend AOPOD for those who are very interested in these atmospheric physics based phenomena.
JohnD wrote:
owlice wrote:
JohnD wrote:Four rainbows?

I can see a complete circle around the Moon, and an arc between it and the horizon.
Where are the other two?

John
Four halos, not rainbows. Please see this image, to which the text links, for a labelled version.

Thnaks, Owlice, but unconvincing.

The inner halo (apologies) is labelled both 22degrees and Circumscribed, and the outer arc the 46 degree halo and the infralateral arc.
That is astronomical legerdemain!
Nothing up my sleeves! Look! Abracadabra! Two haloes become ......... Four haloes!


But re-reading the original description, I note "Elongating the 22 degree arc horizontally is a circumscribed halo" Is this the tangential array touching the 22 halo at approx four oclock, and spreading outwards? I took that for very high cloud. Which I suppose it is, but as such unremarkable.
And the "(third) rainbow-like arc 46 degrees from the Moon and appearing here just above a picturesque winter landscape" is paired with "part of a whole 46 degree circular halo is also visible" as the fourth halo. Two for the price of one - a bargain!

I'm glad to accept if you say so, that the tangential cloud is the second halo. A straight, not round halo, but anyway.

And that two different sorts of ice crystals can cause different effects, with the same "distant tumbling ice crystals" cause the third and fourth haloes? In the same relationship around the Moon, so it's difficult to accept that this is more than one phenomenon, a total of three haloes. Remarkable enough by themselves, but please explain further why four - I'll be most grateful.

John

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by JohnD » Mon Dec 03, 2012 5:21 pm

postscript.
I've seen the link from Chris: http://www.atoptics.co.uk/halo/46orsup.htm and am even less convinced that it is a circumscribed halo we see.
In the link's pics, those are a defined arc which, er, arc away from the internal halo, like an astrological Mercury sign.
John

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by Chris Peterson » Mon Dec 03, 2012 5:28 pm

florid_snow wrote:Then the 46 degree halo, more often called the circum-horizontal arc
The 46° halo and circumhorizontal (or circumhorizon) arcs are different phenomena. They are not synonymous.
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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by florid_snow » Mon Dec 03, 2012 5:31 pm

Definitely lots of confusing terminology. In some cases the circumscribed halo can have arc like shapes (like an astrological Mercury sign, good analogy). But not in all cases, sometimes it is just an almost circular halo with an oval-like bulge towards the sides. Here is a good picture of one:

http://www.atoptics.co.uk/fz472.htm
JohnD wrote:postscript.
I've seen the link from Chris: http://www.atoptics.co.uk/halo/46orsup.htm and am even less convinced that it is a circumscribed halo we see.
In the link's pics, those are a defined arc which, er, arc away from the internal halo, like an astrological Mercury sign.
John

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Re: APOD: A Quadruple Lunar Halo Over Spain (2012 Dec 03)

Post by florid_snow » Mon Dec 03, 2012 5:34 pm

Chris Peterson wrote:
florid_snow wrote:Then the 46 degree halo, more often called the circum-horizontal arc
The 46° halo and circumhorizontal (or circumhorizon) arcs are different phenomena. They are not synonymous.
Getting corrected by Chris is like a dream come true, I always appreciate reading your clear comments on here. Did a bit more reading and understand my error now. One thing I learned is that the 46 degree halo is much more rare than the CHA. Does anyone know if the CHA could be described as a 44 degree halo?