Halo?

It's always worth looking up every so often because there are often surprises when you least expect it. Saturday was a nice summer's day, warm but not hot and with a fair few clouds. However when I got home from shopping I saw a very well pronounced arc of a halo. It's not something I've seen too often, especially with the sun high in the sky, so I had to get the camera out.

* These pictures were taken from London on the 11th July 2015 at 11:40 BST.

So, what's going on here? There's quite a bit on the internet about the science of halos. On this day there was a lot of high level cirrus cloud as well as the Cumulus in the pictures. The ice crystals in the high-altitude cirrus are perfect for creating these optical effects.

It could have been a 22' circular halo, which is the most common. However, the sun in this case wasn't in the centre of the arc; it was instead just off to the top left corner of these pictures. The rule of thumb that 22 degrees is the size of your outstretched hand at arms length also wasn't quite right here, as well as the fact that there was no red/blue hues on the inner and outer edges and the inner sky didn't appear darker.

On the left of the arc as seen here there was a tiny hint of a red/blue spectrum (seen best in the top image). So putting this together with the rest of the observations perhaps I was seeing a Parhelic circle. The small spectrum being a fragment of a 22' halo intersecting it.

A Parhelic circle is rarer than the 22' halo and caused by millions of vertical ice crystals reflecting the sun's light.

I'm no expert and perspective can play tricks so I'm not a hundred percent confident in this but it does make some sense (to me at least!)

Never look directly at the sun. Also, a camera will likely suffer damage when the sun is high and never, ever look through a SLR viewfinder or other optics at the sun.