The Brocken Spectre appears when a low sun is behind a climber who is looking downwards into mist from a ridge or peak. The "spectre" is the shadowy figure - the glow and rings are of course a glory centered directly opposite the sun at the antisolar point. But how is the ghostly figure produced? It is no more than the shadow of the climber projected forward through the mist. All shadows converge towards the antisolar point where the glory also shines. The sometimes odd triangular shape is a perspective effect. The Brocken Spectre is a similar effect to anti-crepuscular rays and cloud shadows.

The spectre sometimes appears to be huge. This is probably caused by the presence of the glory and the mist obscuring more familiar reference points with which to judge its size.
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The Brocken, or Blocksberg, is the highest peak in the Harz Mountains in Germany and also the highest peak of northern Germany. Although its altitude (1,141 metres) is below alpine dimensions, its microclimate resembles that of mountains of 2000 m altitude. The peak tends to have a snow cover from September to May, and mists and fogs shroud it up to 300 days of the year. The mean annual temperature is only 2.9 °C.

The Brocken has always played a role in legends and has been connected with witches and devils; Goethe took up the legends in his Faust, in which he also referred to the mountain. The Brocken spectre is a common phenomenon on this misty mountain, where a climber's shadow cast upon fog creates eerie optical effects.
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