this post was submitted on 25 Nov 2023
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The Moon just now in the UK. No idea what is creating the halo

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[–] [email protected] 3 points 11 months ago (1 children)

the much rarer 46° halo

If that's the really huge halo that seems to take up most of the sky, I've only seen that perhaps 3x in my life.

Are they not collectively called coronas, in your part of the world? They are here.

[–] [email protected] 3 points 11 months ago* (last edited 11 months ago) (2 children)

Yeah that's the one! Only seen it once (coinciding with a supermoon which was frankly surreal).

Coronas are a bit different I believe, though another one of the same group. I've always just called them their individual names, with coronas being tighter and more spectrally-distorting than halos. Maybe the only other collective name I've heard would be the minimally descriptive "atmospheric phenomenon" but that's no fun at all.

Edit: Just took a brief look and indeed coronas are related but formed by refraction through water droplets rather than ice crystals! Cool to know!

[–] [email protected] 3 points 11 months ago (1 children)

Not refraction, but diffraction and interference. The droplets (or ice particles or in some cases even pollen) get so small that light stops behaving like rays at those scales.

[–] [email protected] 1 points 11 months ago

Ahh yes, that's the one! Thank you

[–] [email protected] 1 points 11 months ago

Thanks, that's interesting! Colloquially they're just called coronas here I think, but it sounds like a misnomer.