It was possible in Vespucci's time to calculate latitude quite accurately. A sailor could tell how far north or south he was by measuring the angle between the horizon and a star, or the sun, and then looking up his position in a book. On the other hand, finding longitude (east-west location), was extremely difficult.
Vespucci worked out a way of calculating longitude. First of all he had to find a place where he could see eastern and western horizons. Then he would measure the time from sunset to sunrise with his hour glass, for several nights, to see how much shorter or longer nights were getting. This would allow him to calculate midnight. Next he would start looking at the stars to find a conjunction (the moment when a particular star or planet was passed in the sky by another). Finally, he would have to look in his almanac to know when that conjunction was due to happen in his home port. That would help him to figure out the time difference and the distance, at a rate of 15 degrees for every hour.
It was easier for Amerigo Vespucci to find the...
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| Latitude | |
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