Lunar Halos

Second Question:


Date: Fri, 10 Feb 2006 16:41:28 EST

Subject: the moon


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Hello - I wonder what this is?


tonight  the moon has a huge circle of light, after a completely clear very dark circle closer to the moon then there is a huge light circle some distance from the moon coming after the dark circle I have never seen anything like it, also - not going through the moon in fact missing it all together there are two lines of light going through the darker circle but joining the huge circle of light, very strange but very beautiful, I would love to know what has caused this, and if there is a name for it.


Answer to Second Question:


Date:  Sat, 11 Feb 2006 16:30:23 -0500

Subject: Re: the moon

From: "Eric Canali"


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Glenn, et al:


It sounds like a regular 22 degree lunar halo (the "huge"one described),

but she is also commenting on a "dark"  nimbus holding closer to the

moon. The "dark" she is describing may be the visual effect of the ice

crystals also sorting-out an area of predominantly reddish light close

to the moon, it's quite close if it's what I have in mind... only a

couple moon diameters wide -? - Sometimes these effects are seen along

with the big haloes, yet more often it is not. Sometimes though the

little reddish nimbus occurs without the big 22 degree halo being there

at all.


Also, do remember that the primary halo, out at 22 degrees, is in

itself a "hole" in the field of scattered light coming from the moon

through the blanket of airborne ice crystals... A "hole", yes, it's a

sharp drop-off point, inside of which there is much less scattered

light getting to our eye than one finds immediately at and after the 22

degree boundary. For my whole description of this process, refer to my

little essay on haloes on your website.


As for the "lines" she mentioned -we'd need a lot more description from

her than what we have so far - ideally, a drawing.



Pittsburgh PA

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