Halo, a cirrostratus cloud caused by high level ice crystals around the sun over Sydney . Picture: Bob Barker Source: The Daily Telegraph
A halo is a distant cousin of the rainbow which is caused by sunlight shining through water droplets.
It is a phenomenon which forms as sunlight is refracted in ice crystals suspended in the atmosphere. The sun shines through a thin cloud cover, up about 9km above sea level, where the temperature is between minus 30C and minus 35C.
When I used my Pentax Optio without a filter and reduced the gamma these weird and wonderful impressions were created.