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Unusual Solar Arc

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About this observation
Observer
Peter Tickner
Time of observation
18/02/2020 - 11:13
Object
Unusual reversed colour arc in a contrail above the Sun
Observing location
Urban Berkshire
Equipment
Apple iPhone 11 Pro Max
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I was standing outside my observatory in the garden when I noticed this unusual effect high above the Sun apparently in a contrail.  It doesn't seem to match the common effects such as Sun Dogs or irridescence in clouds near the Sun.  The colours are reversed to a Circumhorizonal effect and above not below the Sun.  If it doesn't have a name for now I am calling it Tickner's Anticircumhorizonal arc!

Comments

Peter Meadows's picture

Nice photo - I think it is a Circumzenithal Arc (see https://www.atoptics.co.uk/halo/cza.htm) which have the same colour order as in the photo.

Peter the Fraudfinder's picture

I did consider that but everything I've checked says that only happens below - not above - the Sun.

Peter

Peter the Fraudfinder's picture

On further research I think that this is a partial Supralateral arc.  They are usually brightly coloured, above at approximately the height of a circumzenithal arc and often mistaken for them, but circumzenithal tend to have much paler colours.

Peter

Honor Wheeler's picture

Having imaged many atmospheric optics over the years, this is indeed a partial Circumzenithal arc, 'zenithal' meaning seen above your zenith i.e. the point above your head. CZ's are always seen above the Sun were as a circumhorizontal arc is always seen below the Sun. Quite often aircraft contrails create the same size ice crystals to give this strong concentrated colour. A supralateral arc doesn't have such an intense colour, they are a weaker form and are rarely seen in the UK.

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