SEXTANT
The sextant is an instrument that was created to determine the angle
between the horizon and a celestial body such as the Sun, the Moon, or a star.
In other words, the sextant measures the altitude of a celestial body.
The sextant is also used in celestial navigation to determine latitude
and longitude.
This device consists of an arc of a circle, marked off in degrees, and a
movable radial arm that pivots at the center of the circle.
A telescope that is lined up with the horizon is mounted to the
framework. To
measure an angle, the image of the body is reflected from the index mirror to
the mirror half of the horizon glass and then into the telescope.
The radial arm is moved until the celestial body is reflected into a
half-silvered mirror in line with the telescope.
You can then read the angle from the arc of the sextant.