HORIZONTOSCOPE developed by F. Tonne

The horizontoscope is a simple, highly efficient precision instrument for determining direct sunlight exposure times. It was developed at the Institut für Tageslichttechnik Stuttgart in the 1950’s.

In combination with sun charts that were also developed by the institute, the horizontoscope can be used to visually record the daily sun exposure times for the entire year at a point of interest. It takes existing structures in the form of buildings, terrain and vegetation into consideration.

Method of operation: The environment is viewed in a stereographic projection on a sun chart (or photographed) through a transparent shell (with precisely calculated curvature) with partially reflective surface from one viewpoint.

The horizontoscope is used in architectural and town planning, but also in the planning of solar systems and in biology and forestry.

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