The number of hours of sunshine in a day is recorded on an instrument called a parheliometer. A solid glass ball focuses the Sun’s rays on to a strip of card. The intensified rays leave scorch marks on the card, moving along as the Sun moves through the sky. The longer the marks, the longer the period of sunshine.
A sunshine recorder is a device that records the amount of sunshine at a given location or region at any time. The results provide information about the weather and climate as well as the temperature of a geographical area. This information is useful in meteorology, science, agriculture, tourism and other fields. It has also been called a heliograph.
There are two basic types of sunshine recorders. One type uses the sun itself as a time-scale for the sunshine readings. The other type uses some form of clock for the time scale.
Older recorders required a human observer to interpret the results; recorded results might differ among observers. Modern sunshine recorders use electronics and computers for precise data that do not depend on a human interpreter. Newer recorders can also measure the global and diffuse radiation.
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