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These properties led to their use as a maritime navigational aid and the subsequent invention of similar devices in the medieval era such as the backstaff, astrolabe, and sextant.
More than 30 nautical and maritime artefacts will be showcased at South Tyneside College, including ship models, celestial globes, chronometers, azimuth compasses, sextants, octants and backstaff dating from 1730 to the 1920s.