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.


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


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-
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.

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.

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).