## Autentic ## - Ross London Brass Sextant - ## Scarse ##

Zululand Coins

## Autentic ## - Ross London Brass Sextant - ## Scarse ##

Comes in wooden Box Similar to This one

A sextant is an instrument generally used to measure the altitude of a celestial object above the horizon. Making this measurement is known as sighting the object, shooting the object, or taking a sight. The angle, and the time when it was measured, can be used to calculate a position line on a nautical or aeronautical chart. A common use of the sextant is to sight the sun at noon to find one's latitude. See celestial navigation for more discussion. Held horizontally, the sextant can be used to measure the angle between any two objects, such as between two lighthouses, which will, similarly, allow for calculation of a line of position on a chart.

The scale of a sextant has a length of ¹⁄₆ of a full circle (60°); hence the sextant's name (sextāns, -antis is the Latin word for "one sixth", "εξάντας" in Greek). An octant is a similar device with a shorter scale (¹⁄₈ of a circle, or 45°), whereas a quintant (¹⁄₅, or 72°) and a quadrant (¹⁄₄, or 90°) have longer scales.

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Aaron, according to the Lens Collector's Vade Mecum the TeleRos series were introduced by Ross of London in about 1923. It was a 5 element design with a 3 + 2 group configuration. It was made with and without a shutter. The 12 inch focal length version is said to suit 4x5.

Andrew Ross founded the firm in 1878. They made both their own design lenses (such as your TeleRos) and also manufactured Zeiss lenses particularly the Tessar type. Ross continued to make lenses throughout the first half of the 20th century.