record number: | 44 |
instrument type: | sextant |
manufacturer: | Josh Semalvico London |
serial number: | 650 |
weight: | 1.35 kg |
dimensions (l/w/h): | 31/12/25 cm |
year of manufacture: | 1890 |
instrument set up: |
on three legs when not in use handle, held in hand when measuring |
The sextant was made around 1890. It is held in the hand with a wooden handle when taking measurements. The reading of the division on the silver-plated metal bracket shall be by means of a vernier with a lens, providing the graduation unit of 15''. The crosshairs consist of two horizontal and two vertical hairs which together form a rectangle. The instrument has a movable mirror with filters for taking a sight of the Sun. It measures the angle between the Sun and the horizon, and with additional data from the almanac and a known instant of the Sun's position, the geographical position can be determined.
The instrument was completely restored, polished and lacquered in 2017.
Characteristics
vertical circle | ||
---|---|---|
diameter: | unprotected, part of a circle with a division from 0° to 140° | |
type of division: | engraved division | |
limb implementation: | silvered metal bracket | |
division: | sexagesimal/sexadecimal | |
unit: | 15' | |
Reading | ||
number of reading points: | 1 | |
reading device: | vernier | |
number of units: | 60 | |
graduation unit: | 15'' | |
Telescope | ||
diameter of objective: | 16 mm | |
type: | Ramsden's retractable eyepiece | |
cross hairs/reticule: | two horizontal hairs intersecting with two vertical hairs, aiming through the middle of the rectangle |