www.antik.it/Nautical-antiques/7992-Antique-Sextant/
1729007680Code 7992 Antique SextantBrass sextant signed G. Inch 62 Wapping London from around the mid-19th century, housed in its beautiful original mahogany wood box shaped like the instrument, with brass clasps and hinges, complete with lock and original key. A brass plate fixed to the outside of the lid is engraved with the initials P.D.O. Edge and vernier in engraved silver, ebony handle, 3 colored glasses for the fixed mirror and 4 for the mobile one, three telescopes, one of which is long, a microscope for reading the vernier graduated from 0 to 120°, index mirror and of horizon. Box measures 28x29.5x13 cm – 11x11.7x5.1 inches. Complete with support base made to measure in wood and brass. In good condition, with signs of ancient repairs on the lid of the box.
The sextant is an optical instrument used in astronomical navigation to measure the height of the stars above the horizon, in order to obtain the geographical coordinates relating to the ship's point. It has the shape of a circular sector of 60°, i.e. one sixth of the circumference, hence the name, at the vertex of which is pivoted a mobile alidade on which a mirror is fixed which rotates with it. On the back of the mirror there is a support with a telescope oriented towards a second mirror, silvered only for one half, which allows you to simultaneously observe the sea horizon, in alignment, and the pointed star, whose image is reflected by the fixed mirror to the alidade and then to the silver part of the mirror. By adjusting the position of the alidade index it is possible to make the image of the horizon collimate with that of the celestial body and obtain the angle between the horizon and the celestial body on the graduated scale of the 60° sector. To measure the height of a star (for example the Sun) with a sextant, place the instrument on a vertical plane and, looking through the sighting device, sight the horizon line visible through the non-silvered half of the fixed mirror. By moving the alidade, with which the mirror is integral, the light rays coming from the celestial body and subsequently reflected by the mobile mirror and by the silver half of the fixed mirror are sent back by the latter in the direction of observation: if you look through the aiming device, you see the image of the star, obtained by double reflection, coinciding with the horizon line. The height of the star is expressed by the angle whose value is read on the graduated scale. The filter is used when the star to be targeted is the Sun.
It was Sir Isaac Newton who invented the principle of double reflection in navigational instruments, but this research was never published. Subsequently, two men, independently of each other, discovered the sextant around 1730: John Hadley (1682-1744), English mathematician, and Thomas Godfrey, (1704-1749), American inventor. But it was not until 1758 that Admiral John Campbell carried out a series of sea trials to test a new method that relied on lunar distance as a means of calculating longitude. This is how the sextant was developed. Initially made of brass, they had scales divided with great precision by mathematicians who built scientific instruments.
FAQ
Do you provide an authenticity certificate/expertise?
Of course! The legislative decree n. 42/2004 stipulates that who sells works of art or historical and archaeological items has the obligation to deliver to the purchaser the documents attesting to the authenticity of the object, or at least to submit the documents relating to the probable attribution and origin. Antik Arte & Scienza provides an expertise (as warranty) that contains a description, period and assignment or the author, if known, of the item.
How can I pay?
Secure payments by PayPal, credit card or bank transfer.
What are the shipping terms and the delivery schedule?
Shipping by DHL or UPS is free (but if we are shipping to a country non-EU remember that any taxes and customs duties are on your expense), and items will be sent just after receiving of payment.
Italy: delivering on the average in 24 h.
Europe: delivering on the average in 2/3 weekdays.
Other countries: delivering on the average in 5 weekdays; custom duties charged to the buyer.
Is shipping insured?
Of course! Free insurance by Lloyd's London that covers almost all destinations.
If I change my mind, can I return the item?
Of course! (see our general terms for more information).
e-Shop
Nautical antiques
Code 7992 Antique Sextant
Antik Arte & Scienza sas di Daniela Giorgi - via S. Giovanni sul Muro 10 20121 Milan (MI) Italy - +39 0286461448 - info@antik.it - www.antik.it - Monday-Saturday: 10am-7pm
