Items Similar to Burnished brass sextant D. Mc Lean & Co Lta 113 Frenchurch St. London 1890

A poket sextant signed Stanley, London 1890.

WW1 brass pocket military sextant made by Ryland & Sons, London circa 1915

Brass sextant signed Imray & Son 89 & 102 Minories London mid-19th century

English Brass Telescope on Tripod Stand signed Dollond, London Circa 1890

Burnished brass earth globe - Circa 1930s

Antique English Brass & Glass Elegant Compass by Spencer & Co London

Want more images or videos?

Request additional images or videos from the seller

1 of 21

Burnished brass sextant D. Mc Lean & Co Lta 113 Frenchurch St. London 1890

About the Item

Burnished brass sextant D. Mc Lean & Co Lta 113 Frenchurch St. London, datatable around the end of the 19th century, instrument complete with optics and housed in its original square-shaped mahogany box with hinges, locking hooks and handle in brass. Brass frame with engraved silver goniometric scale embedded in the arch, with scale from 0 to + 150, silver flap and vernier, wooden handle, 3 colored glasses for fixed mirror and 4 for movable mirror, three telescopes, sun filter and adjustment key, a microscope for reading vernier, index and horizon mirror. A label on the inside of the box lid indicates that the instrument was serviced in 1914. Box size cm 26x23.5x12.7 - inches 10.3x9.3x5. Conservation status: very good, complete with stand base made of custom wood and brass. The last photo is the gift box. The sextant is an optical instrument used in astronomical navigation to measure the height of the stars on the horizon in order to derive geographical coordinates relative to the ship's point. It is in the shape of a circular sector of 60°, that is, one-sixth of a circumference, hence the name, at the apex of which is pivoted a movable alidade on which is fixed a mirror that rotates with it. On the back of the mirror is a stand with a telescope oriented toward a second mirror, only one half of which is silvered, making it possible to simultaneously observe the sea horizon, in alignment, and the pointed star, whose image is reflected by the mirror attached to the alidade and subsequently by the silvered part of the mirror. By adjusting the position of the index of the alidade, it is possible to collimate the image of the horizon with that of the star and to derive on the graduated scale of the 60° sector the angle between the horizon and the star. To make a sextant measurement of the height of a star (for example, the Sun), one places the instrument in a vertical plane and, looking through the sighting device, aims at the horizon line visible through the unsilvered half of the fixed mirror. Moving the alidade, with which the mirror is integral, causes the light rays coming from the star and subsequently reflected by the moving mirror and the silvered half of the fixed mirror to be 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, coincide with the horizon line. The height of the astro is expressed by the angle whose value is read on the graduated scale. The filter is used when the star to be looked at is the Sun. It was Sir Isaac Newton who invented the principle of double reflection in navigation instruments, but this research was never published. Subsequently, two men, independently of each other, discovered the sextant around 1730 : John Hadley (1682-1744), an English mathematician, and Thomas Godfrey, (1704-1749), an American inventor. But it was not until 1758 that Admiral John Campbell carried out a series of offshore trials to test a new method that relied on lunar distance as a means of calculating longitude. This was how the sextant was developed. Initially made of brass, they had scales divided with great precision by mathematicians who made scientific instruments.

Dimensions:

Height: 3.5 in (8.89 cm)Width: 9.3 in (23.63 cm)Depth: 10.3 in (26.17 cm)

Materials and Techniques:

Brass

Period:

1890-1899

Date of Manufacture:

1890

Condition:

Wear consistent with age and use.

Seller Location:

Milan, IT

Materials

Brass

1890 Small Antique Nautical Brass Pelorus Boyce-Meyer Pelorus Bronxonville N.Y

$1,164

Antique Late 19th Century English Scientific Instruments

Materials

Brass

A poket sextant signed Stanley, London 1890.

$1,978

WW1 brass pocket military sextant made by Ryland & Sons, London circa 1915

Located in Central England, GB

This rare precision instrument is a fine solid brass pocket sextant made for the military by the high-quality instrument makers Ryland & Son Ltd of London. It dates to the early 20th...

Category

Early 20th Century British Edwardian Scientific Instruments

Materials

Brass

WW1 brass pocket military sextant made by Ryland & Sons, London circa 1915

$801

English Brass Telescope on Tripod Stand signed Dollond, London Circa 1890

Located in Charleston, SC

English brass telescope on tripod stand with slipper feet. Telescope has the original carrying case with lens covers. Late 19th Century

Category

Antique 19th Century British Scientific Instruments

English Brass Telescope on Tripod Stand signed Dollond, London Circa 1890

$7,000

Burnished brass earth globe - Circa 1930s

Located in Linkebeek, BE

Burnished brass earth globe - Circa 1930s Globe - World map Measures : 20x18cm H:25cm Wear consistent with age and use

Category

20th Century Maps

Materials

Brass

Burnished brass earth globe - Circa 1930s

$488

Antique English Brass & Glass Elegant Compass by Spencer & Co London

By Spencer & Company

Located in San Diego, CA

Beautiful elegant compass circa 1970's in solid brass with glass bt spencer & Co.

Category

20th Century English Hollywood Regency Aviation Objects

Materials

Brass

Antique English Brass & Glass Elegant Compass by Spencer & Co London

$225

Boyle’s Patent Air Pump Ventilator, London, 1890

Located in Milan, IT

Boyle’s patent air pump ventilator mahogany wood, glass an iron, depicting architecture model. Robert Boyle & son Ventilating engineeres. London & Glasgow, end XIX century.

Category