Glossary

	Glossary	A B C D E F G H I J K L M N O P Q R S T U V X Y Z
A	Altitude	the angular elevation of a celestial object, i.e. the sun above the horizon
	Aphelion	the farthest point of earth to the sun; this point is reached at about the 4th of July. Aquarius - the Water carrier, one of the 12 zodiacal constellations.
	Aries	the Ram, one of the 12 zodiacal constellations.
	Armillary	from Latin; it means bracelet or iron ring, Also used for an old astronomical instrument composed of rings showing the positions of important circles of the celestial sphere.
	Astrology	the divination of the supposed influences of the positions of the stars and planets on human affairs. Astrology is not a science.
	Astronomy	the science concerned with the study of objects outside the earth's atmosphere
	Axis	the imaginary line around which an object rotates.
C	Cancer	the Crab, one of the 12 zodiacal constellations.
	Capricornus	the He-goat, one of the 12 zodiacal constellations.
	Ceiling dial	hour lines are drawn on the ceiling
	Co-latitude	= (90° - latitude)
	Constellation	a configurations of stars
D	Declination	the astronomical equivalent of terrestrial latitude
	Diptych	a folding sundial that traditionally was made from ivory or boxwood
E	Earth	one of the nine planets that revolve around the sun. Earth has one moon.
	Eccentricity	of an ellipse. The measure of how non-circular the ellipse is.
	Equation of time	the difference between the mean time and apparent or solar time the maximum difference is 16 min 24s.
	Equator	the line that bisects the earth, half way between the two poles.
	Equinox	means equal night, when the sun is on the celestial equator, night and day are of equal length. This happens on 21 March and 23 September.
F	Focus	of an ellipse. One of two points that determine the eccentricity of the ellipse.
G	Gnomon	is of Greek origin and means inspector or indicator. The gnomon is also called the style.
	Galaxy	is of greek origin and means milk. A galaxy is a collection of stars, interstellar gas and dust of which our solar system is a part Our galaxy is called the Milky Way galaxy.
	Gemini	the Twins (Castor & Pollux), one of the 12 zodiacal constellations.
	Geographic address	latitude and longitude.
	GPS	Global Positioning System. An instrument which communicates with satellites to determine your exact position - longitude, latitude and height above sea level.
H	Helio- chronometer	means sun clock
		Horizon - is of Greek origin and means where the sea and sky meet.
	Hour	The earth rotates around its own axis in 24 hours. 1 hour = 60 minutes.
I	Io	moon of Jupiter
J	Jupiter	the largest planet of the solar system. It has 4 moons.
L	Latitude	the latitude of any other point on the surface of the earth is the angle subtended by the centre of the earth between that point and the equator.
	Leo	the Lion, one of the 12 zodiacal constellations.
	Libra	the Balance, one of the 12 zodiacal constellations.
	Longitude	the longitude is the angular distance (east-west) from the standard meridian. The earth takes 24 hours to rotate around its axis once, therefore 15° represent 1 hour.
M	Mars	one of the smaller planets of the solar system.
	Mercury	the innermost planet of the solar system and always seen close to the sun.
	Meridian	the true north-south line.
	Minute	1 minute = 60 seconds. 60 minutes = 1 hour.
N	Nautical mile	is the length of an arc along a meridian subtending an angle of 1 minute, hence it is in practical terms 1 minute of latitude. At the equator a nautical mile is 1,843 km and at the poles it is and 1,862 km.
	Neptune	is the planet the second farthest from the sun and takes 165 years to complete 1 orbit.
		Nodus - a specific point on the style which traces out the path of the sun.
	North, magnetic	magnetic north is to where a compass would point. It is not the same as true north since the magnetic field of the earth is not perfectly aligned with the planet’s poles.
	North, true	to find true north, place a piece of paper onto level ground. Place a stick (or pencil) upright on the paper and mark the end of the shadow every 15 or 30 minutes around noon time. True north is where the shadow is the shortest.
O	Orbit	the path of the earth around the sun.
P	Perihelion	the closest point of of earth to the sun; this point is reached on the 4th of January. The earth-sun distance on that day is about 147.5 million km.
	Pinhole	a small hole made by a pin or as if made by a pin.
	Pisces	the Fishes, one of the 12 zodiacal constellations.
	Pluto	is the planet the furthest away from the sun and takes 248 Earth years to circle the sun once.
	Poke	middle english for pocket.
	Pole	the end points of an axis. Planest have a north and south pole.
R	Radius	the radius of a circle = half the diameter.
S	Sagittarius	the Archer, one of the 12 zodiacal constellations. Saturn - the most beautiful planet of the solar system, well known for its rings.
	Scaphe	Scaphe is from the ancient greek for boat.
	Scorpius	the Scorpion, one of the 12 zodiacal constellations.
	Seasons	The seasons on Earth are caused by the 23.5° tilt of Earth's axis. During southern summer the south pole is tilted towards the sun and Earth is closer to the sun than during southern winter.
	Second	60 second = 1 minute, or 60 second = 1° (as for angle measurements).
	Solstice	a turning point. Summer solstice is when the sun has reached it's most southern point (on 22 December), winter solstice is when the sun has reached it's most northern point (on 21 June).
	Style	is origin is Latin and the word means stake or pole.
	Substyle	the base of the gnomon.
	Sun day	the longest day is on 21 December, the shortest on 21 June. Day and night are equal on 20 March and 23 September.
T	Taurus	the Bull, one of the 12 zodiacal constellations.
	Time, apparent	also called real solar time, is the real time according to the sun. The apparent time differs from place to place.
	Time, mean
	Time, standard	the time according to your clock .
	Time, universal
	Time zone	The earth is divided into 24 time zones. Each zone corresponds to 15° of longitude.
U	Uranus	one of the outermost planets of the solar system. Uranus is visible to the naked eye.
V	Venus	is the second closest planet to the sun and, as Mercury, is always seen close to the sun.
	Vernal	is from the latin vernalis. Ver in latin means spring. The vernal equinox is the equinox in spring.
	Virgo	the Virgin, one of the 12 zodiacal constellations.
Y	year	the time it takes the sun to travel around the sun once (1 year = 365 days 6 hours).
Z	zenith	the point vertically overhead in the celestial sphere.
	zodiac	an imaginary zone in the sky, 18° wide, in which the sun, moon and planets move, also called the circle of animals. The constellations that move in this path are given a special meaning. There are 12 of theses zodiacal constellations, mostly named after animals: Aries (the Ram), Taurus (the Bull), Gemini (the Twins), Cancer (the Crab), Leo (the Lion), Virgo (the Virgin), Libra (the Balance), Scorpius (the Scorpion), Sagittarius (the Archer), Capricornus (the He-goat), Aquarius (the Water carrier) and Pisces (the Fishes).