Solid Brass Nocturnal with Hardwood Stand $33
This is a full size faithful solid brass reproduction of the nocturnal, which was an early sea-faring navigational instrument.
The nocturnal or "night disc," was used in navigation to calculate the latitude and the time at night.
First described in 1272, this simple method of latitude determination using the nocturnal continued to be improved upon until its use faded in the late fifteenth century.
The nocturnal is elaborately decorated and has a shape roughly similar to that of a hand mirror.
Corresponding to the months of the year, the circumference was divided into twelve equal parts.
An "index" or "pointer" pivoted from the disc's center.
During use, the nocturnal was placed at arm's length with the North Star Polaris visible through a hole in the center.
The second brightest star in Ursa Minor, Kobach, which circles the pole star Polaris, is aligned with the pointer.
The nocturnal’s scale would yield a correction in arcminutes, to be applied to Polaris.
If the slight distance of Polaris from the true pole was not compensated, it could result in a 50-mile error.
The nocturnal was also able to determine the time from the celestial clock that rotates around Polaris.
Scales around the perimeter were used to set the month and day.
The readings taken would yield the time.
The nocturnal measures 4 1/2 inches (11.4
cm) in diameter, 5 1/2 inches (14.0 cm) tall, and weighs a solid 9.1 ounces (258 grams).
The hardwood base is 4 1/2 inches (11.4 cm) wide and 2 1/8 inches (5.4 cm) deep.
The Solid Brass Nocturnal with Hardwood Stand is available for only $33.
We also carry solid brass Astrolabes.