What was the instrument that measured the positions of the stars which enabled sailors to calculate a ships latitude?

Answer 1

There were a number of instruments developed over the course of the centuries to make it possible to measure the angular elevation of celestial bodies above the horizon. Interestingly enough, the names of the various devices denoted the proportion of a circle that the object covered.

The earliest was the "quadrant"; a right-angle viewing line with a quarter circle of arc, and calibrated in degrees. Line up the viewing arm with the star, and a plumb bob would display the angular elevation. This didn't work very well at sea, because the motions of a ship would move the plumb line off vertical, and it wasn't very accurate. The word "quadrant" comes from the latin word for "one fourth".

They improved this device with the "octant", one eighth of a circle, but with a mirror and an improved measuring device. "Octo" is the latin prefix for eight.

The current angular measuring device is the "sextant", where "sextus" is the latin word for six. The sextant has an arc of one sixth of a circle. An improved mirror lets you line up the Sun, Moon or star with the horizon, eliminating the need for a plumb bob, and a precise measuring calibration makes it possible to measure the altitude of an object to within a minute of arc.

Answer 2

Latitude is measured by a sextant and the north star

Longitude is measured by an accurate clock and the sun-rise

Answer 3

A sextant. To measure longitude, you also need an accurate watch.

Answer 4

Most likely a 'sextant', This measures the angles between celestial objects (stars) and is then related to latitude and longitude on a map.

Answer 5

It is called an Astrolabe, or a Sextant