One Sunday afternoon in September 2005 at Chennai , I observed a halo around sun as you see in the photograph below:

I remember having seen the halo around moon also. I remembered what I read in the camera manual that shooting directly the sun that too with a digital camera will damage the sensor, I shot this photograph such that the building coverd the sun.

Later I learnt from the website http://www.atoptics.co.uk/halosim.htm that the phenomenon is called Ice Halo. Tiny ice crystals in the atmosphere create halos by refracting and reflecting light.Ice halo displays range from the familiar circle around the sun or moon to rare and prized events when the whole sky is webbed by intricate arcs. Halos bestow a delicate beauty to the skies and tell us about the crystals inhabiting the clouds.