Aurora borealis

The aurora borealis is formed by the collision of charged particles in the magnetosphere with atoms in the Earth's upper atmosphere. Every winter I try to photograph this phenomenon from Old Slains Castle, near Collieston, Aberdeenshire, NE Scotland, where there is very little light pollution. I use a Canon EOS 10D digital camera with 17-40 f4L lens. The fun is the fact that, with a long exposure of about 30 seconds, you have to guess when and where the best lights will appear and you never quite know what the photograph will look like. Green and red colours are formed by emissions from oxygen, while blue and purple are formed by emissions from nitrogen. All of these images were taken from my garden at around midnight, mostly on two episodes of particularly strong auroral activity in October-November 2003, when the night sky was lit up in glorious technicolour for several nights in a row.