A heliograph or sunshine recorder (aka Campbell-Stokes recorder) - from which this kaleidoscope is derived - is a device that records the amount of sunshine at a given location. The glass sphere – typically 10 cm (4 inches) in diameter – is designed to focus the rays from the sun onto a card mounted at the back and is set on a stand. The card is held in place by grooves of which there are three overlapping sets, to allow for the altitude of the sun during different seasons of the year. In the northern hemisphere the winter card is used from 15 October to 29 February, the equinox card from 1 March to 11 April and 3 September to 14 October. The summer card is therefore used from 12 April to 2 September. Each card is marked as to the hour, with local noon being in the centre, and is read in 10ths. In the northern hemisphere, the unit is set in a stand facing south to enable the maximum amount of sun to be recorded.