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Perpetual Calendar
Only perpetual calendars meet the basic condition of permitting the deduction of any essential data from any other data (year, month, week and day). However, all the analogue perpetual calendars known are hardly perpetual since the limit of their calculations is about 50 years.
Our calendar starts at January 1, 1600, and ends at December 31, 2799. It is based on a repeating cycle of 400 years and a solar cycle of 28 years. It works by means of the "Dominical letter".
£35
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Nocturnal and Tide Computer
The piece is a replica of a Nocturnal and Tide Computer from 1570, signed by Humphrey Cole. Currently this instrument can be found in the British Museum, London.
One of its faces is a Nocturnal and the other is a Tide Computer. The Nocturnal or star clock is an artifact that is used to obtain the time at night using the fixed stars in the sky. The abacus or tide computer is used to figure the time of the tides that greatly affect navigation both in harbours and for fishing.
£48
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Quadrant Capuccino
The name is derived from the best known version of this solar clock, in which the path of the pearl
in both tropics traces two lines that resemble the hood of Capuchin monks. The quadrant goes back to the 15th century, although the date is not precise.
This model is a sea-going, local-hour quadrant of a type called a clinometer.
It is a reproduction and has been calculated for a latitude of 51.5º N
£38
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Lunar and Tidal Computer
Use this beautiful lunar calendar to determine the phase of the Moon and to explore the relationship with the tides.
Diameter 100mm, thickness 8mm.
£38
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Sextant
This instrument is a reproduction of an Octant of the mid 17th century. By semi-accurately measuring the height of stars or the sun, the Octant allows navigators to determine geographic latitude.
In 1731 John Hadley (England) and Thomas Godfrey (Philadelphia, U.S.A.), demonstrated the Octant, independently. The arc of an Octant is 45º or 1/8 of a circle (hence its name) and is divided into 90 parts each ½ degree. The Sextant (1757) replaced the wood frame with metal and progressively took the Octant´s place. It is still used today.
£140
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Tide Computer keyring
This is one face of the Nocturnal and Tide Computer above - the Tide side!
The abacus or tide computer is used to figure the time of the tides that greatly affect navigation both in harbours and for fishing.
Please see 'Resources - Articles' for an explanation of Tide Computers.
£21
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