Sunshine recorder lens (seen here with bowl AST0770). Inscription on bowl in Latin 'HORAS NON NUMERO NISI SERENAS' reads "I count only the hours that are serene".

On box 'Temperate Sunshine Sphere Met.Ref. No 192 Mo.1546/150 Focal length 2'946 Diameter 3'982 Tested by....Date 16.5.50 Ref no. D5511F Chance Brothers Limited Lighthouse Works Smethwick C.B.Ltd.'

Sunshine recorders are positioned on a local meridian (north-south line) and record the number of hours of sunshine. Each day, a new card strip is placed into the grooves behind the glass sphere. As the Sun crosses the sky, the sphere acts as a magnifying lens, burning a line into the card that’s specially designed to scorch rather than burst into flames. The strip varies in length and position according to the seasons.

The idea was first devised by John Francis Campbell in 1853 and was later developed by the physicist Sir George Gabriel Stokes in 1879. Although simple to use and easy to maintain, the instruments are susceptible to variable results and need human intervention to replace the card strip each day, hence modern meteorological observatories rely on electronic sensors instead.