Reflection

2.3 The sextant

Determine the position of an object using a device that contains a system of plane mirrors.**

The sextant is a device with many uses. Sailors use it to determine their distance from shore by measuring the angle of elevation of a lighthouse. As the height of lighthouses can be found in tables, a quick tangent calculation will give the horizontal distance from shore.

The sextant is also used to determine one's position out at sea. In this case, the sun, moon, or Ursa Major can be used as a reference point. Navigation tables transform these data into meridians and longitudes. The calculations are relatively uncomplicated.

For ages, astronomers have calculated the movement of the stars with a sextant. Here's a good topic for your T.M.S.project - collect data on the motion of Mars and Venus. The results will really surprise you!

Suggested activity: Use a sextant along with a topographical map in order to determine your position in a large space (telemetry).

1. Choose three landmarks that you recognize on the map. One should be a point directly facing you because it will help you to draw a reference line.
2. Next, in relation to this reference line, use the sextant to measure the angles between your position and each of the other two points.
3. Draw a straight line from the landmark towards your position, and then draw lines on the measured angles from the other two points.
4. Your position will be at the intersection of the three lines. Use the map's scale to determine your distance from the points.

Uses of the sextant