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Moon dog

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#1 JeanB

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Posted 07 January 2013 - 11:21 AM

Hi everyone,

it has been a while since I posted a sketch here. I have been very busy and had to neglect my hobby.

However, I came to see the sketches from you guys from time to time.

In december I spent some time in Cuba. And I had the chance to see for the first time a ring around the moon (moon dog). It was spectacular. The ring is a perfect 22 degrees circle. On the 27th Jupiter was also included in the ring. I decided to sktech the view on my note pad and work on it with pastels and GIMP software back home.

here is the result.

Jean

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#2 niteskystargazer

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Posted 07 January 2013 - 11:26 AM

Jean,

Very good sketch of the Moon Dog :).

CS,KLU,

:thanx:,

Tom

#3 Aquarellia

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Posted 07 January 2013 - 12:04 PM

Whaw Jean, that's art for which you have to buy a frame...
That's really a nice pastel, thank you for sharing
Michel

#4 Andrev

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Posted 07 January 2013 - 12:20 PM

Michel.

I told exactly the same to Jean ehehehe.

Andre.

#5 Ed D

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Posted 07 January 2013 - 09:51 PM

Jean, that's a really nice sketch. You captured it well. We get moon dogs every so often down here in Miami. BTW, you were in the small city/province where I was born many moons ago.

Ed D

#6 maroubra_boy

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Posted 07 January 2013 - 10:07 PM

Lovely work, mate! There's a certain refreshing quality to this piece, Jean. I've found myself lingering over it... :)

Alex.

#7 frank5817

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Posted 07 January 2013 - 10:49 PM

Jean,

I love it. It has a real tropical look to it too.

Frank :)

#8 drbyyz

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Posted 07 January 2013 - 11:47 PM

Awesome sketch! The trees make it special, gives it some extra personal touch that brings me into your experience. Love it.

Saw one of these a week or two ago and tried to snap a shot with the iPhone since I didn't have anything else on me, but it didn't work out too well.

#9 JeanB

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Posted 08 January 2013 - 09:10 AM

Thank you guys! Your comments are much appreciated.

If I understand correctly, this phenomenon is common in the south part of the world. Interesting.

I was also impressed to read that this ring is due to tiny hexagonal ice crystals in the cirrus in altitude and that we may see a second ring of 46 degrees when condition are perfect. Well you south-friends should try to sketch that one of these nights to show us north-fellows what it looks like.

Jean

#10 Chopin

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Posted 08 January 2013 - 09:22 AM

Jean, a spectacular illustration. I agree that the tree gives a nice touch.

#11 Jef De Wit

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Posted 09 January 2013 - 08:38 AM

I like it!

#12 PeterDob

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Posted 09 January 2013 - 09:10 AM

Really beautiful, Jean!

Peter

#13 JeanB

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Posted 11 January 2013 - 02:37 PM

Jason, jef, Peter,

thanks guys for your comments!

Jean

#14 JimPie

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Posted 13 January 2013 - 01:50 PM

Wonderful sketch. What cool phenomenon.

#15 GlennLeDrew

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Posted 21 January 2013 - 05:42 AM

Very evocative; the palm really provides an interesting perspective. I like it!

A couple points of fact:

A Moon (or Sun) dog would be a somewhat horizontally elongated brightening at the radius of the halo, at the same altitude as the Moon, and where the parhelic circle intersects the 22 degree halo. They occur when the Moon (Sun) is not too high in the sky. What you observed here is just the 22 degree radius halo.

There is not necessarily a preponderance of parhelia in southern latitudes; they occur worldwide, whenever cirrostratus cloud or suitable low level ice crystals in cold airmasses occur.

Given the 22 degree radius, or 44 degree diameter of the halo, it's apparent that at this scale the 1/2 degree Moon, which is a mere 1/88 the halo's size, should be rendered as much smaller. Actually close to the size of the dot representing Jupiter. The impression imparted here, for anyone who may not have seen a halo, is that the halo is quite a bit smaller than it really is.

#16 Special Ed

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Posted 21 January 2013 - 10:31 AM

Jean,

You made a lovely impression of the lunar halo from a tropical setting. :)

Glenn is correct about the nomenclature and size of the halo. You can learn a lot more about this and other atmospheric phenomena at Les Cowley's website.

The old timers called this a "ring around the Moon" and said that the number of stars one could count inside the ring foretold how many days it would be before rain.

This had some basis in fact because the more water vapor was present in the atmosphere, the fewer stars one would see. :cool:

#17 JeanB

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Posted 21 January 2013 - 10:41 AM

Many thanks Glen and Michael,

I guess it was not easy for me to reproduce the correct proportions on this sketch,but you are right: the ring should have been larger.

Jean

#18 JeanB

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Posted 21 January 2013 - 11:11 AM

On the other hand, I checked at some ring around the moon pictures on the web, and the proportion look close to what I have sketched.

Any explanation? Even if I take into account the effect of the brightness of the moon on its apparent size it looks as if the proportion are skewed. I am right?

http://en.wikipedia....nd_the_moon.JPG

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#19 Gregen

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Posted 21 January 2013 - 03:20 PM

Beautiful sketches!

#20 mike73

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Posted 21 January 2013 - 04:12 PM

Hey Jean Cuba's a great place isnt it?

I saw a moon dog from the UK last Febuary, I thought my eyes were playing up at first but we definately had a moon dog a couple nights in a row.

Its a lovely sketch and as others have said the trees in the foreground really add to the picture.

#21 GlennLeDrew

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Posted 21 January 2013 - 10:36 PM

Jean,
The image you posted immediately above *appears* to be a drawing, not a photo (but I could be wrong.) That notwithstanding, the Moon's disk is blurred, not sharp-edged, and so could be taken to be due to diffusion of light by the cloud layer. The lunar disk will be quite a bit smaller than this fuzzy blob of light.

A photo which clearly reveals the dimmer halo will necessarily greatly overexpose the Moon, which even in the absence of cloud could result in something of a 'bloating' effect. And the scatter induced by the ice crystals will only accentuate this.

The math is pretty clear. A 1/2 degree Moon can only be 1/88 as large as the 44 degree diameter halo. It would be instructive to make a correctly scaled sketch to see this.

In your original drawing, it's not that the halo is undersized, but rather that the Moon is oversized. This is a virtually universal mistake. Look at how huge the Moon is usually made in the movies, for instance. The root cause is this. The very bright Moon appears relatively larger than it is compared to dimmer phenomena.

Try this. Next night out, look at the two pointer stars in the bowl of the Big Dipper (which point the way to Polaris.) By your best estimate, how many full Moons do you suppose could fit side by side between these two stars? As for myself, even knowing the answer I have to really convince myself that some 10 Moons could fit, not the 4 or 5 that my eyes mistakenly suggest.

Perhaps even better; compare the Pleiades with the Moon. The Moon appears to be larger than the whole cluster, but the Mooon can actually fit inside the 'bowl' of this miniature dipper.

#22 JeanB

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Posted 22 January 2013 - 09:51 AM

Excellent information, Glenn! :graduate: Thank you very much. Indeed the math is quite straightforward. I looked at many photos of the moon dog and they all seem to oversize the moon. However you are quite right, in all these photo the moon is blurred and overexposed.

I will keep that in mind the next time!

Many thanks again.

Jean






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