Navigating the Journey

Navigational instruments
Navigational instruments: sextant, ship's log, marine compass and telescope.
Source: Museum Victoria

Navigating the route to Australia was a complex task, requiring great skill on the part of the ship's captain, as well as the use of various navigational tools. These included the telescope, marine compass, ship's log and sextant. However, navigation was also dependent on the ship's captain having a good working knowledge of the position of the stars in the night sky.

Telescopes were an essential tool of marine navigation for examining sightings of land more closely and for identifying ships passed en route. This was especially important in times of war.

The compass is an instrument used for determining the direction in which a ship is travelling. It consists of a freely moving magnetised needle, which indicates magnetic north.

The introduction of iron hulled ships such as the Great Britain created complications for the use of the compass. The metal in the hull of these ships interfered with the behaviour of the magnetic needle, requiring special adjustments and calculations to be made for accurate readings.

Charts and navigation maps were developed by the Admiralty for the use of British naval and merchant ships. Detail and accuracy were very important, and many are still in use today. Charts and maps were always kept in the chartroom on board the ship.

A sextant is an astronomical instrument used for taking latitude readings, by measuring the angle of altitude of the sun, moon or a star above the horizon at sea.

A chronometer is a timepiece that is able to keep accurate time on board ship. It enables mariners to calculate longitude by observing the position of certain stars in the sky at specific times, and comparing their observations with the data contained in a nautical almanac.

A Ship's Log looked very similar to a torpedo but was used to measure the speed of a ship. When dragged behind the vessel, movement of water past the propeller caused it to rotate, turning the small needle dials to record the distance and speed travelled.

Webquest

Use the internet to prepare a short presentation on one of the following navigational instruments: Telescope, Compass, Sextant, Chronometer, Ship's Log.

Search:
'measuring instruments' at Powerhouse Museum collection http://www.powerhousemuseum.com/collection/database/
or 'navigational instruments' at National Maritime Museum (UK) http://www.nmm.ac.uk/collections/explore/index.cfm/category/astronomical

Describe when the instrument was developed, how it works, and its importance for navigators. Find a suitable picture or diagram of the instrument to illustrate your presentation.