A sextant is an instrument generally used to measure
of a celestial object above the horizon
Making this measurement is known as "sighting the object,"
"shooting the object," or "taking a sight." The angle, and
the time when it was measured, can be used to calculate
a position line on a nautical or aeronautical chart. A
common use of the sextant is to sight the sun at noon
to find one's latitude
. Held sideways instead of upright,
the sextant can be used to measure the angle between any
two objects, such as between two lighthouses, which will,
similarly, allow for calculation of a line of position
on a chart.
Do it yourself Sextant or CD-Sextant: