Navigation Instruments of the 17th Century
On the far left is a Nocturnal which was used to measure the time at night. The instrument has two superimposed, rotating discs with a pointer and a hole in the middle. On the one disc with the months of the year, the date is set. Through the hole, the polar star is aimed at and the pointer is placed on the pole pointer of Ursa Major. The time can then be read on the second disc.
Right next to it is a compass with a sundial and behind it a lodestone. The lodestone, a piece of magnetite which is magnetic by nature, was vital in the first centuries of navigation to ensure that the ship’s compass worked properly. Until the mid-18th century, when improved compasses were developed, compass needles lost their magnetism quite quickly and had to be re-magnetised by stroking the length of the needle with a magnetic stone. The lodestones were often mounted in frames of brass, bronze or silver and sometimes had an iron or steel holder - a rod to maintain their magnetic force.
In front of it there is a quadrant that works like an astrolabe. Here you only measure the height of the pole star to determine its position. See the star or the sun along an edge, from the tip of the quadrant. A piece of rope hangs from there. The piece hangs down because of the attached weight (called plumb line), and the scale crossed by the rope indicates the angular height of the body. With this information they could determine their latitude. Disadvantage, the scales were only valid for a certain measured and noted region, so that the use of the instrument at sea was limited.
The last object is a divider, which was used to measure distances on maps and was able to determine how far it was still to the ship’s destination and how far the ship had already sailed.
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