Nocturnal or nocturlabes, as they were sometimes called, are devices for telling the time of night. their operation is based on the fact that the stars while remaining fixed relative to one another, appear to rotate around the North star (Polaris)It is of course the earth which is rota- ting and the Polaris remains fixed because it lies along the earth´s a- xis of rotation. As the others stars appear to rotate, their position at any moment indicates the time. Sometimes called “horologium noctur- num” or “Nocturlabe”. It´s related to the astrolabe and the sundials. The mention of a dedicated instrument for its measurement are not fo- und before the Middle Ages. The earlier image presenting the use of a nocturnal is in a manuscript dated from the 12th century. Raymond Lull repeatedly described the use os a “Sphera horarum noctis”. With Martin Cortés de Albacar´s book “Arte de Navegar” published in 1551 the name and the instrument gained a larger popularity. Timekeeping was very important to navigators at sea. Precise time was needed to use tide tables to safely enter harbours and also to regulate work shifts aboard.. Thus, the navigators were able to tell the time at night if ther weather was clear. The problem was that in foul weather, when the sky was obscured, they had no way of knowing the exact time except by the running of the sand-glasses. By the middle of the 18th century more accurate clocks started to become available known as chronometres and the nocturnals fell out of use. Nocturnals are really simple analogue computers. Compared to others instruments which requiere mathematical tables and trigonometry, the nocturnal is simple to use. Our noctolabe is ready to work with three constellations: Ursa Major, Ursa Minor and Cassiopeia. Is made of old brass plated metal. The support is made of wood and is presented in a beautiful perfect case to make a memorable gift. It is accompanied by a booklet with all the historical accounts and instructions for use.
Height (including throne) 13 cm
Diameter: 9.5 cm
Thickness: 0.5 cm
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