What did I see?

[MalcolmM]

I was out walking this evening, light cloud and a fairly full moon up quite high.

There was a large bright halo round the moon. It was roughly the thickness of the moon, maybe a bit more and it's radius was about twenty degrees (thumb nail to little finger nail of spread hand at arms length).

Anyone know what this is, what causes it and how common it is?

Thanks,

Malcolm 

[Cornelius Varley]

It's called a Moon dog. Light from the Moon is refracted by ice crystals in the atmosphere/clouds causing the halo.

[Floater]

1 hour ago, Cornelius Varley said:

It's called a Moon dog. Light from the Moon is refracted by ice crystals in the atmosphere/clouds causing the halo.

Not sure this is accurate, Peter.

It would be a 22° halo, caused as you describe. But a moondog/moondogs would be one or two bright spots at the side(s) similar to sundogs which often appear along with such a halo. I think moondogs are rarer than sundogs but the 22° halos on the Moon are common enough, given the required atmospheric conditions.

Always willing to be corrected, though. 

Edited January 5, 2023 by Floater

[MalcolmM]

8 hours ago, Floater said:

Not sure this is accurate, Peter.

It would be a 22° halo, caused as you describe. But a moondog/moondogs would be one or two bright spots at the side(s) similar to sundogs which often appear along with such a halo. I think moondogs are rarer than sundogs but the 22° halos on the Moon are common enough, given the required atmospheric conditions.

Always willing to be corrected, though. 

Thanks for the replies. This was definitely a full continuous halo. No obvious bright spots.

[Mr Spock]

A moon halo. There's an explanation here https://en.wikipedia.org/wiki/22°_halo

[Cornelius Varley]

9 hours ago, Floater said:

Not sure this is accurate, Peter.

It would be a 22° halo, caused as you describe. But a moondog/moondogs would be one or two bright spots at the side(s) similar to sundogs which often appear along with such a halo. I think moondogs are rarer than sundogs but the 22° halos on the Moon are common enough, given the required atmospheric conditions.

Always willing to be corrected, though. 

I stand corrected, as the man said in his new orthopaedic shoes.

 

 

 

 

 

 

 

I'll get my coat.

[MalcolmM]

3 minutes ago, Cornelius Varley said:

I stand corrected, as the man said in his new orthopaedic shoes.

 

 

 

 

 

 

 

I'll get my coat.

I'm standing corrected in my new 'toe rocker' shoes but they make me walk like a Thunderbird's puppet!

Malcolm

[MalcolmM]

51 minutes ago, Mr Spock said:

A moon halo. There's an explanation here https://en.wikipedia.org/wiki/22°_halo

Thanks @Mr Spock and a  bit of maths too ... fantastic 🙂

Malcolm

[Leo S]

Best web site for ice halo identification and atmospheric optics info in general: http://www.atoptics.co.uk/