Sundial

Museo della Civiltà Contadina del Friuli Imperiale (Sundials courtyard)    

Photo n° 5

Illumination is the greatness equivalent to the irradiation on the field of visible light, when the diverse sensibility of human eyes to the various colours has to be taken into account. The unity of measurement to calculate the intensity of the illumination that hits a unitary surface is the lux (lumen/m2).

The two quadrants show the trend of the hemispheric solar irradiation and of the corresponding illumination, referred to the surfaces of the quadrants themselves, with clear skies and standard atmospheric conditions according to UNI-EN and ASTM norms.