Sunshine Cards

They can be used to help build a climate profile of an area and have also been used to provide information to the tourist industry.

For a great many years the instrument for measuring sunshine duration was the Campbell-Stokes sunshine recorder. The original instrument (heliometer) was invented by John Francis Campbell in 1853, but the later card-holding version was developed by Sir George Stokes in 1879.

A glass sphere focuses sunlight on a graduated card and the length of the burn trace on the card corresponds to the duration and intensity of sunshine at a given location.