Occasional Weather Equipment Feature – The Campbell-Stokes Sunshine Recorder.
This is the Campbell-Stokes Sunshine Recorder. It’s essentially a big glass ball that focuses the sun’s rays onto a curved calibrated card and burns a trace when the sun is out.
The length of the burn mark is then measured against the scale on the card, revealing the length of bright sunshine hours per day.
The card is changed every day in manned observing stations. The CSSR has been replaced by electronic sensors on modern weather stations and allows them to be unmanned.