sextant,the stars,to navigate by,how!in laymans terms,please!!?(ocean scenarios)?

Answer 1

Latitude is how far North or South of the equator you are. The sextant is used to measure this by measuring the angle of the pole star above the horizon. The nautical almanac is a book which contains charts which are used if other star's elevation is measured. Altair seems to be the one which is used as the reference. The altitude of the sun when due south at mid day is also measured but would need correcting for time of year.
Longitude is how far East or West one is. Until the late 18th century there was no way of doing this. Charles II built the Greenwich observatory to research this. There is a method using observations of the moons of Jupiter but it is not practical to make the measurements on a ship at sea but was used by surveyors on land.
The measurement of Longitude became possible when sufficiently accurate clocks became available at the end of the 18th century. The sun is due South at noon so the time at Greenwich is compared with the time of local noon, for example if the chronometer showed 3pm at local noon you would be 45 degrees West. In practice the nautical almanac combines these measurements so if you make a measurement and know the time you can find your position.
The use of radio time signals in the 20th century avoided the reliance on clocks which one had no way of checking for months
Using technology developed during WWII the DECCA and LORAN systems were made available. A radio receiver on the ship measures the time difference between synchronised signals received from 3 land based transmitters.More recently sattelite navigation has become available and computers do the work of the charts and Nautical Almanac.

Answer 2

The sextant was used to measure the angle between the sun and the horizon at mid day to determine longitude of a ship. For this you needed an accurate clock. George Harrison was one of the first to make such a clock.
This is why most people kept close to the shore so they could see landmarks.
Now substitute a star in the sky for the sun and measure its angle. Tables were calculated and provided to mariners which gave the angles of various stars at - for example - midnight.
That's how they did it.
Latitude was a bit more of a problem as was cloudy weather.
Cloudsley-Shovel ran the British fleet onto the rocks of the Scilly Isles by getting it wrong.
When a sailor pointed out to him that he was about to do this he had him hung from the yard arm.
RoyS.

Answer 3

To navigate at sea you need to know your longitude and latitude.
You can get latitude (how near you are to the north pole) by measuring the angle of the pole star against the horizon and for this use a sextant. If you want to know how far round the earth you are then a measure the angle of the sun, with the sextant, against the horizon at it's highest and you then compare the time that happens with Greenwich mean time and the difference tells you how far round the earth you are. To do this you need to have accurate time pieces before they had those they measured by dead reckoning. Checking their speed with a log and rope of knots and allowing for the drift of the current. Needless to say they were often many miles out

Answer 4

The sextant is a device to find ones latitude, by shooting the sun during the day, or a known star at night.
The celestial object is brought down to the horizon, by the instrument to measure latitude.

Longitude is not so easy, and it is that which required an accurate timepiece or chronograph to find.

Answer 5

There are many sources of information to help you here's one: http://www.reedsalmanac.com/