Campbell Stokes Sunshine Recorder – Tropical
This instrument is manufactured to the specifications of the British Meteorological Office and is used extensively by government meteorological services world wide. In 1964 it was adopted by the World Meteorological Organisation as their Interim Reference Recorder for use in all member countries.
The sphere, made of well-annealed colourless optical glass is securely clamped on a semi-circular metal arc by means of two bosses attached precisely across a diameter and located by an adjusting screw onto the ball ended boss. Also mounted on the arc is a bowl of spherical section machined from gunmetal.
This bowl has the shape of a belt cut from a hollow sphere and contains three overlapping pairs of grooves in which record cards suitable for different seasons can be inserted and secured by a screw. The metal arc is mounted in a grooved slide to permit the inclination of the sphere and bowl to be adjusted for geographical latitude.
The slide is mounted on a T-shaped metal base which is supported on levelling screws on a fixed metal sub-base.
Interpretation of Records
The record cards are made from a special board with a matt turquoise finish on which even weak sunlight produces a clearly visible trace. They are treated to char rather than burn so that the trace produced by strong sunlight does not spread significantly.
There are three types of card to correspond to the behaviour of the sun at different seasons: long curved for use in summer, straight for use near the equinoxes and short curved for use in winter.
All are marked with hourly intervals, and may be used in either the northern or the southern hemisphere and the slide is mounted on a T-shaped metal base which is supported on levelling screws on a fixed metal sub-base.
Adjustment for latitude: 0° to 40° N or S Sphere: 102mm +/- 1.3mm diameter. Focal length for sodium D light, 74.9mm +/-0.25mm
Dimensions: 240 x 187 x 165mm Weight: 4.3kg