Sunshine recorder
Sunshine Autograph, also called heliograph, is a simple device for measuring the duration of sunshine a day.
Operation
It consists of a large glass ball, which acts as a magnifying glass. In the spherical focal surface behind the ball, in which the light rays maximum bundle is a plastic or paper strip attached with timing marks. In sunshine the sun is point-like in plastic or paper strip, over the time course of the sun hence resulting in focal lines. Based on the time stamp can later be accurately determined, seemed at what time and how long the sun. To determine the daily sunshine duration, the lengths of the burned lines are added.
The heliograph is not to be confused with the model developed by the French physicist Claude Servais Mathias Pouillet Pyrheliometer, formerly called Pyroheliometer, literally: sun fire meter.