Sun filter from sextant
Maker
Spencer, Browning and Rust
(British, 1784 - 1840)
Date1784-1840
Object number00006890
NameSextant part
MediumBrass, darkened glass
DimensionsOverall: 8 x 24 x 24 mm
ClassificationsTools and equipment
Credit LineANMM Collection
Purchased with USA Bicentennial Gift funds
DescriptionThis brass lens with darkened glass is a sextant accessory. It belongs to a brass sextant issued with the serial number 2334, which was made by Spencer, Browning and Rust in London.HistoryThe sextant was developed in 1757. It is an instrument of double reflection by means of two mirrors, and thus although its actual arc subtends an angle of 60 degrees (1/6th of a circle - hence the name sextant), it is capable of measuring angles up to 120 degrees. The sextant was an improvement on the earlier quadrant, an instrument capable for measuring angles up to 90 degrees (1/4th of a circle hence the name quadrant). The capacity of sextants to read angles greater than 90 degrees was an advantage when using the lunar distance method to determine longitude. This was also useful for taking horizontal angles.
SignificanceThis sextant accessory is representative of the high level of technological development achieved in the design and manufacture of navigational instruments in the 19th century.
Parent (child)/Child (parent)