• Records duration of sunshine.
• Accurate measurements.
• Simple to use.
This instrument is used to record the duration of sunshine each day. The sun's rays are focused by a precision glass sphere onto a curved card. The intense heat burns a trace on the card. As the sun moves across the sky, so does the position of the spot across the card. If the sun is obscured by cloud then no trace is made. At the end of the day, the length, less gaps, is proportional to the duration of sunshine.