In earlier times, marine sextant had
a fixed telescope leveled on the horizon and a radial arm is moved against an
arc scaled in degrees. The radial arm is adjusted to get the reflection, of a
known star, from index mirror and then off the horizon mirror down the telescope
until it lines up with the horizon. The position of the radial arm on the scale
gives the stars elevation. The nautical sextant range includes: slow motion nautical
sextant, octants, slow motion nautical sextants and round dubble telescope nautical.
In modern navigation sextants, the light ray from the celestial body
is reflected in two mirrors (in series) one of which is adjustable and the other
is half silvered. By rotating one mirror and its attached index bar, the image
of the body is brought down to the horizon. The rotation measures the altitude
on the limb.














