This instrument consists of a perpetual lunar calendar on one side and an abacus or tide calculator on the other. It is based on the need to to predict the time of the passage of the Tides and the intimate relationship of these with the influence of the rotation of the Moon in its orbit around the Earth.
Knowing the phases of the moon is of great cultural importance for many peoples: calendars, religious festivals, agricultural practices, etc. The tide calculator or abacus is used to calculate tide times because of its important effects on navigation, ports and fishing.
In order to develop this instrument Hemisferium analyzed several instruments of the XVI and XVII centuries (like those of the English School and H. Cole among others) such as astronomical compendiums, volvelles or abacuses in which they tried to determine a method to perform these calculations.
Maximum Height: 16,2cm / Diameter: 12cm / Thickness: 0,7cm