Designing Your Character & Other Handy Things 2

Moon Terminology

A

Albedo — This term is a unit-less measure that refers to the how much an object diffusely reflects light from the sun.

Angular Diameter — The measurement of the diameter of a distant  object from the perspective of the angle resulting between the observer  and the object's outer edges.  Also known as the 'visual diameter'.

Annular Eclipse — Refers to an solar eclipse where the Moon is  between the Sun and the Earth, but with the Moon appearing smaller than  the Sun to the observer, leaving a bright ring around the circumference  of the Moon.

Anomalistic Month — The length of time that the Moon takes to  pass between perigee (or apogee) passages — that is, the 27.55455 day  period during which the Moon moves from its closest (or farthest) point  to the Earth, all the way around and back again.

Anorthositic Rock — A calcium-rich rock type found in abundance on the Moon.

Aphelion — The farthest point from the Sun in a planetary body's orbit.

Apogee — The farthest point from the Earth in the Moon's orbit.

Apogean Tide — The name for low tide when the Moon is at it's farthest point from the Earth.

Apolune — The farthest point from the Moon in an object's orbit around it.

B

Basalt — Volcanic rock formed by rapidly cooling lava. Found on the moon and the earth.

Breccia — A type of rock that is composed of a matrix of  different materials, minerals and fragments of other rocks. Found on the  moon and the earth.

C

Celestial equator — The projection of the Earth's equator into  space.  It could be considered an invisible belt that surrounds the  Earth in the minds of astronomers.

Celestial Mechanics — The specialized areas of astrology that describes the gravitational effects of heavenly bodies as well as their motion.

Colongitude — Also called selenographic colongitude, it is the longitude of the Moon's morning terminator.

Conjunction — The term applied when two planets are in close  proximity to each other in the sky, from the perspective of an  Earth-bound observer.

Crater Wall — The cliff-like wall formed by the impact of a meteor with a celestial body such as a planet or moon.

Crescent Moon — The famous image of the Moon frequently used in  the media, consisting of only a thin crescent slice of the Moon being  visible from Earth.  This phase of the moon occurs just after the New  Moon phase, which is also known as Dark of the Moon.  There is also a  Crescent Moon phase just prior to the next New Moon as well.

D

Dark of the Moon — So named because during this phase, the Moon is not visible in the sky, Dark of the Moon is also known as New Moon.

Declination — Declination is the position of a celestial body,  such as the Moon, in the equatorial coordinate system.  Declination is  measured by degrees in relation to the celestial equator.

Diurnal — In astronomy, diurnal generally refers to the motion of  an object in a 24 hour period.  An example would be Moon-rise.  These  activities repeat every 24 hours.  The diurnal arc describes the amount  of time a celestial object takes to transition from fully risen to fully  set.