Compass, chronometre, sextant, log and sea charts are in principally all a navigator needs to determine position and follow a set course.
In older days, navigation was imprecise. Near the coast, navigators could rely on various landmarks to determine their position but out at sea they were more vulnerable. Even if the sailors had access to instruments such as compass, quadrant and astrolabe, these aids were not always reliable. When weather conditions prevented astronomical observations, sailing by dead reckoning was the only option. The captain calculated how far the ship had travelled from a certain point and then estimated the direction of travel. Based on this he drew a line on the chart and reach an estimated position. This was a very unreliable method since there were so many factors that could affect the outcome: currents, waves, winds, calculation errors and the difficulty of keeping to a set course in heavy seas.
Advanced astronomical navigation developed rapidly during the 18th and 19th centuries. The understanding of the compass and of magnetic declination and deviation deepened. The sextant and the chronometer were invented, both necessary to determine latitude and longitude. The chronometer, which de facto is a normal watch, was a particularly significant invention as it made it possible to reliably determine longitude at sea. The scope of the longitude problem was such that the British parliament in 1714 signed the Longitude Act, in which a prize was promised to whomever invented a reliable method for calculating longitude at sea. The problem was eventually solved by watchmaker Johan Harrison, who in 1761 presented the chronometer H4, a seaworthy precision watch, to the Longitude Board. H4 and its three predecessors can be seen at the Royal Observatory in Greenwich, UK.
The instrument room displays our extensive collection of navigational instruments. In addition to the obvious sextants and chronometers we also show lesser-known instruments, such as the azimuth, salinometer, hydrometer and anemometer.
The night sky that adorns the ceiling in the instrument room is one of the building’s original features. The two domes represent the north and south skies and among the brass constellations you can find both the Stella Polaris and the Southern Cross.