Navigation Glossary
Introduction | Contents | First Chapter >>
This Glossary of Navigation introduces and defines a number of useful terms that the Mariner must be familiar with.
The names of certain things are necessary to be known by all mariners or seafarers, who wish to practise Navigation, and they include: the names of circles of the Sphere, and what they are, and their uses; and also the names of other things belonging thereunto, and what they are, and their uses.
The Horizon Circle
The Horizon is the parting of the earth or the Sea and the sky, that is to say, the half of the heavens being above over your head, and the other half hidden by the earth or the sea under them; and this Horizon circle does move as you move: for as you travel and change your place, so does the Horizon change in all points.
The Use of the Horizon Circle
The use of the Horizon circle is this: to take the height of the sun or any star, with the cross-staff, setting one end in line with the Horizon, and the other end with the Sun or the star, so that you have a true Horizon; and that must be done upon the sea, or upon level ground on the top of a hill, otherwise it is no true Horizon. And also if the Sun or Moon, or any star is to be seen, they must also be above the Horizon; if they are not to be seen, then they are under the Horizon.
The Meridian Circle
The Meridian is a circle beginning due South, and so passing by your Zenith (that is, right over the crown of your head) and heading due North, and so connecting the two Poles of the world; and if you travel due South or North, you do not change your meridian; but in going any other way, you change it.
The Use of the Meridian Circle
The Meridian circle is used to know the exact time of noon by the Sun; for as soon as the middle of the Sun is upon the Meridian, then it is noon, and when the Sun, Moon, or any Star is upon the Meridian, then they are farthest from the Horizon, and it is a good time to take their height so as to know the altitude or height of the Pole, whereby you may perfectly know how far you are to the North or South of any place.
The Equinoctial Circle
The Equinoctial is a fixed circle in the Heavens equally distant from both the Poles, and passes directly over the middle of the earth. It is called the Equinoctial, for if the Sun is there, then throughout the world the Sun is twelve hours above the Horizon and twelve hours under the Horizon, saving the two Poles for there the Equinoctial is at one with the Horizon, so they shall see half the Sun and no more, until the Sun departs from the Equinoctial. Also for those that live on the Equator, which is directly under the Equinoctial, the Sun, the Moon, and all the Stars will be twelve hours above the Horizon and twelve hours under it, at any time of year.
The Use of the Equinoctial Circle
The Equinoctial is used to know what declination the Sun or any other Star has from it, and on which side, and by that know the height of the Equinoctial, and from that, the height of either of the two Poles of the Worlds.
The North Tropic Circle
The North Tropic is the greatest declination that the Sun comes Northwards, and at that time are our longest Summer days and shortest nights. This tropic is a circle parallel to the Equinoctial. Here the Celestial Pole is at an altitude of 23 ½ degrees at all times.
The South Tropic Circle
The South Tropic is the greatest declination that the Sun goes Southwards, and at that time are our shortest Winter days and longest nights. This tropic is a circle parallel to the Equinoctial. There is little use for these two circles in Navigation, being more an Astrological phenomenon.
The Arctic Circle
The Arctic circle is the southernmost part of the earth for which the sun stays above the Horizon during an entire day in midsummer, and does not rise for at least one once day during deepest winter. It is a circle parallel to the Equinoctial made by the pole of the Zodiac. Here the Celestial Pole is at an altitude of 66 ½ degrees at all times.
The Antarctic Circle
The Antarctic circle is the southern twin to the Arctic circle, being the northernmost part of the earth for which the sun stays above the Horizon during an entire day in the Antipodean midsummer, and does not rise for at least one once day during their deepest winter. It is a circle parallel to the Equinoctial made by the pole of the Zodiac.
The Celestial Circle
The Celestial circle is centred on the Celestial Pole and touches the Horizon at due North, and so varies according to the place that you are in, widening and narrowing according to the altitude or height of the Pole; for as you go Southwards, then your Celestial circle narrows, until you come right under the Equinoctial line, and then you have no Celestial circle; and as you go Northwards, then your Celestial circle grows wider, and when you stand on the Arctic Circle, there your Celestial circle is co-extensive with the North Tropic circle, and under the Celestial Pole, your Celestial circle is the Equinoctial.
The Use of the Celestial Circle
The Celestial circle is used to know what stars never set for you; for all those stars or lights that you see under the Celestial Pole do not set; and by knowing the position of your stars, you may know your Northing immediately.
The Hidden Circle
The Hidden circle is centred on the Hidden Pole and touches the Horizon at due South, and is opposed to the Celestial circle, for however each circle widens and narrows always the other circle is of the same size; so the Hidden circle does not differ from the Celestial circle, saving that the Celestial circle is above the Horizon and the Hidden circle is beneath.
The Use of the Hidden Circle
The Hidden circle is used to know what stars will never rise above your horizon. When the Equinoctial is to your north, the Celestial Pole is hidden, and the Hidden Pole shows in the heavens; here the roles of the Celestial and Hidden circles are also transferred.
The Zodiac Circle
The Zodiac is the greatest circle in all the Heavens, wherein all the wanderers or planets keep their courses, that is to say the Sun and Moon, the two inferior Aether Worlds Ariel and Freya, and the three exterior Aether Worlds Thunor, Wotan and Hela. The mystery that is Merlyn also stays within the Zodiac, when it is present at all, but should not be relied upon for Navigation. The Zodiac circle is said to be divided into fourteen equal parts, called the fourteen signs, as Smith, Thief, Lover, Warrior, King, Mother, Magician, Wolf, Void, Reaper, Fool, Farmer, Maiden, Messenger, although other places and times have divided them otherwise. This circle stands oblique to the Equinoctial, crossing it at two opposite points: at its northernmost point the centre of the Zodiac reaches the North Tropic circle, and at its southernmost point the centre lies on the South Tropic circle. The Zodiac circle, unlike all other circles, is not a line, extending six degrees to the north and south of its centre, making the Zodiac twelve degrees broad.
The Use of the Zodiac Circle
The Zodiac is used to know in what sign the Sun and Moon and the other planets lie in as they move, and also to know the time of the change of the Moon, with all the other Aspects; and in like manner to know the aspects of all the other planets unto the Moon, and also the planets amongst themselves; and by the aspects in the fourteen signs is gather their effects, and in what country it may happen. Many more properties of the Zodiac are mastered in Astrology, and I leave further matters to those esteemed experts.
The Ecliptic Circle
The Ecliptic circle is the circle lying in the heart of the Zodiac, running through its centre from Tropic to Tropic, along which the Sun travels upon.
The Use of the Ecliptic Circle
The Ecliptic circle is used for tracking the variance of the wanderers through the Zodiac. If the Moon or other planet be to the North of the Ecliptic, it is said they have North latitude, and if they lie to its south, then the have south latitude, and also by this circle is known the eclipse of the Sun and the Moon.
The Seasonal Circles
The Seasonal, or Colour, circles divide the all the parallel circles and the Zodiac into four equal parts, the one of the circles crossing the Zodiac between the King and Mother, and again between Farmer and Maiden and passing through the two Poles of the World is called the Equinoctial circle, and the other circle crossing the Zodiac in the Thief and Void is called the Solstitial circle, and each circle meets the other at the two Poles of the World.
The Use of the Seasonal Circle
The use of the Seasonal circles is that as the Sun passes by them, it divides the year into four parts, and this can be used to precisely locate the Equinoxes and Solstices, being essential knowledge for both advanced Navigation and Astrology. From this, when the Sun lie in the Smith, Thief and Lover it is Summer, the King and Mother are Autumnal, the Wolf, Void and Reaper are Winter signs, and Farmer and Maiden are of the Spring, and the Warrior, Magician, Fool and Messenger are signs of change between these seasons.
The two Poles of the World
The two Poles of the World (that is, the Celestial and Hidden Poles, and their terrestrial counterparts the North and South Poles), are to be imagined as a single axletree, as the one Pole is always aligned directly with the other. The Celestial pole is always above our Horizon, and the Hidden Pole always under our Horizon, being fixed fast in the Heavens, and the Equinoctial lying equally between them. The reason why they are to be seen as an axletree is that the whole Heavens and all the lights of the firmament are carried round from the East to the West in twenty-four hours, so that no light or place remains stationary, except the two Poles of the Worlds around which all else revolves.
The Use of the Poles of the World
The Poles are used as the ends of the measure of latitude, which is to know how far you have travelled, and to know what climate and temperature you can expect.
The two Poles of the Zodiac
The two Poles of the Zodiac, or Ecliptic, are to be imagined as an axletree, as the one Pole is always aligned directly with the other, and the Ecliptic lies equally between them. And the Sun and the Moon and the planets and fixed stars are carried Eastwards in a year according to the standing of the Zodiac.
The Use of the Poles of the Zodiac
The Zodiac Poles are the meeting points of all the meridian lines which are the divisions between the fourteen signs of the Zodiac and also of the four circles of the seasons. The meridians between the Zodiac signs can then be used to classify stars that lie outside the Zodiac according to the signs.
The Zenith Point
The Zenith or vertical point is a point in the Heavens right over the crown of your head, and moves as we do, and is as an axletree to the Horizon circle; for as you travel from one point to another, so your Zenith and Horizon circle move also. And beneath your feet lies its opposite, the Nadir point.
The Use of the Zenith
The Zenith point is used to know how far or near any star is from your Zenith, by taking the true height of the star with an instrument, for the height of the Zenith is always 90 degrees from the Horizon on any side of you.
A Degree
A Degree is the part of a whole circle divided evenly into 360, howsoever big or small the circle is.
The Use of a Degree
Degrees are used to measure and track the course of the Sun and the Moon through the Zodiac, or any of the planets or wanderers, and to know at any time how many degrees they may be apart, or when they have the same aspect (location). And also, degrees are used to know what latitude and what declination any light or star has from the Ecliptic or Equinoctial, and also the degrees will show how many miles you have travelled to the North or South, for every degree is equivalent to 60 nautical miles when travelling North or South, and can be known by the altitude of the Celestial Pole or the number of degrees between the Equinoctial and your Zenith. This can be reckoned as from your Zenith to the Horizon is 90 degrees in all directions, and is half the compass of the visible Heavens, and as the earth hides the other half of the Heavens beneath it, twice of twice 90 makes 360, which is the contents of every great circle in the sky.
A Minute
There are two sorts of Minutes – those of time and of measure, and each is a sixtieth part of a greater time or measure, being Hours and Degrees. So a Minute of time is one sixtieth of an Hour, and a Minute of measure is one sixtieth of a Degree, or a nautical mile. A Minute of either sort can be sub-divided into 60 Seconds.
Altitude
Altitude is the height of any thing. Of Celestial bodies such as the Sun, Moon, Stars, or the various Poles, it is measured in degrees from the Horizon, and of Terrestrial objects it is measured in height from sea level or another level surface.
Latitude
Latitude is the Northing of any thing. Of Celestial bodies such as the Moon or Stars, it is measures in degrees of variation North or South from the Ecliptic, which is the path of the Sun. On the earth, Latitude is the number of degrees of variation from the Equator, wherein the North & South Poles have 90 degrees of Latitude from the Equator.
Longitude
Longitude in the Heavens is of a Celestial body relative to a sign of the Zodiac, and if it be in such a sign, and so many degrees of travel into it, then it is said that they have so many degrees Longitude in that sign. An example being that when the Sun is 13 degrees along in the Void, it is the day of the Winter Solstice. The Sun travels 360 degrees of Longitude through the Zodiac in a year of 364 days, and so each day the Sun progresses one degree of Longitude through its current Zodiac sign, except on the High Holidays, where it is reckoned that the Sun moves not. The Moon, while it travels through it's waxing cycle in 28 days, only takes 26 days to move through the Zodiac, so it moves through a sign in a little less than two days, except that it moves faster and slower depending on the Dragon and its Auge. And Longitude upon the earth is counted from the city of Tycho to the Westwards or Eastwards, that if any town be to the West so many degrees from Tycho, then it is said to be at so many degrees of Longitude West, and otherwise of degrees Longitude East. And Tycho lies on the Prime Meridian, that is, neither East nor West, and that which is exactly on the far side of the earth from Tac is of 180 degrees Longitude, and is neither East nor West. From this Longitude is known the difference in time of day from another location, as for every 15 degrees East one travels, an hour is lost, and the reverse when travelling Westwards, thence travelling to the West always is slightly faster, racing the Sun. Also is known the time of the changes of the Moon, or any other aspect, including Eclipses of the Sun or Moon, at that place.
Declination
Declination is counted only in the Heavens, where if the Sun or any other star is to the North or South of the Equinoctial, then it is said to have so many degrees of declination to the North or South. This is not the same as Celestial Latitude, which is the deviation from the Ecliptic who lies at an acute angle to the Equinoctial as shown above, but Declination is in true correspondence with Terrestrial Latitude.
The Properties of a Circle
Each circle has the same properties, regardless of its size, or if it be Heavenly or not. The Circumference is the encompassing of a circle around its outer edge. The Centre of the Circle is the middle point, equally distant from every edge. The Diameter is the breadth of a circle, passing right over the centre, from outside to outside. The Radius is the size of a circle, from the centre to the outside only. Two circles are Parallel if the closest points on their respective edges are equally distant in every place.
Auge
The Auge is a time where the Moon is furthest in its eccentricity, being nearer the Heavens and further from the earth than is common. To know this point, it is necessary to understand that the Sun and Moon do not travel in a perfect Circle around the earth (or the earth around the sun – it is of no matter which, to we mariners). There path is distorted lengthwise, and its distortion is its eccentricity, measured against the size of the circle it would otherwise travel. When the Moon travels furthest from the earth, this is the Apapsis of its path, and marks the time of the Auge, and when it is closest, this is the Periapsis of its path, and marks the opposition of the Auge. The Auge is used to know when the Moon is moving most slowly, for the closer the Moon is to the earth, the faster it moves. Also, weaker tides occur at the Auge, and stronger at its opposition. On Full and New Moons at the opposition the King Tides occur, leading to much flooding and disaster on the coast, and also rocks that otherwise are deep rise to the surface and rip the hulls of unwary mariners. Thus a good Navigator always knows not just the phase of the Moon, but its times of Auge.
The Dragon
The head of the Dragon Saros is the place where the Moon crosses over the Ecliptic line from South to North, and the tail of the Dragon is where it passes back to the South again. During these times are when there is the greatest chance of an eclipse of the Moon or Sun, and from its crossing times and Auge, one can know of what type and time the eclipse will be.
