A brocken spectre is a shadow cast on the tops of clouds or fog, with a rainbow-coloured halo appearing around the viewer's head. The name comes from a German mountain where they are oftem seen.
There is a bing (spoil heap) about a mile from my house which I can drive to quickly. It is surrounded by moorland and takes only five minutes to climb, so it's a convenient spot to hunt brocken spectres. There needs to be enough fog at low level, with the sun low enough to cast your shadow onto the clouds instead of the ground at your feet.
The pictures below also show fogbows, which are created in the same way as rainbows.
