Heliograph is instrument...

Heliograph is instrument which measures number of sun hours during the day. Sphere concentrates the light into a point, similar to laser, that burns paper ribbon with a time scale on it. There are ribbons for each season, also angle of the sphere changes with each season as days go longer or shorter. This one is in front of Zavizan hut (1594m) meteorological station. In the background is Veliki Zavizan (1676m) while the peak reflected in the sphere is Zavizanska Kosa (1620m). Photo: Aleksandar Gospic