GLOSSARY

Ångström One hundred millionth of a centimetre. Has the symbol Å.

Annular Eclipse A solar eclipse in which the moon does not completely cover the Sun. A ring of sunlight is seen around the black disk of the Moon.

Anomalistic Month Period of time for the Moon to travel from apogee to perigee and back again to apogee.

Aphelion Point in the Earth’s orbit that is farthest from the Sun.

Apogee A point in the Moon’s orbit that is farthest from the Earth.

Ascending Node A point in the orbit of the Moon, or any orbit, when it crosses the ecliptic from below to above the ecliptic plane (see also descending node).

Baily’s beads The breaking up of sunlight, visible at the edge of the Moon’s disk just before the appearance of a total eclipse. Caused by the streaming of sunlight between mountains at the edge of the Moon.

Celestial sphere An Earth-centred model of the heavens in which the motion of the stars, the planets, the Sun and the Moon are projected on to a large imaginary crystal dome.

Central Eclipse A total or annular eclipse.

Corona The hot outer atmosphere of the Sun which appears as a halo during a total eclipse.

Cuneiform The writing used on clay tablets in Mesopotamia during the second and third Millennia BC.

Descending Node The point in the orbit of the Moon when it crosses from above to below the ecliptic.

Diamond Ring Effect The last remaining bead of light of Baily’s beads, which shines just before and just after the total phase of a solar eclipse. It has the appearance of a diamond ring.

Draconic Month The time it takes for the Moon to complete one cycle and return to the same node, the same point where the Moon’s orbit crosses the ecliptic.

Eclipse Season The period when the Sun is close to alignment with a lunar node. This is the period when eclipses may take place, and occurs every 173 days.

Eclipse Year The interval between successive passes of the Sun past the same lunar node, approximately 346.62 days.

Ecliptic The path of the Sun around the sky as it appears from the Earth.

Elliptical Orbit The oval-shaped path of an orbital body circling another attracting body which has a precise mathematical formulation.

Ephemerides Tables of the position of the Sun and the Moon at different times.

Ephemeris A table giving the changing position of any celestial body in an orbit.

First Contact The beginning of a solar eclipse when the edge of the Moon first touches the complete disk of the Sun.

Fourth Contact The end of the solar eclipse when the disk of the Moon completely breaks away from the disk of the Sun.

Geocentric Describing an Earth-centred model of the solar system in which celestial bodies are thought to be revolving around the Earth.

Heliocentric Describing a model in which the Earth and other celestial bodies revolve about the Sun.

Latitude Angular distance on the Earth north or south of the equator.

Longitude Angular distance on the Earth either east or west of the prime meridian at Greenwich.

Lunar Eclipse The appearance of the shadow of the Earth falling across the full Moon.

Node Point in the sky at which the orbital path of the Moon crosses the ecliptic, the path of the Sun.

Partial Eclipse An eclipse in which the observer sees only part of the Sun obscured by the Moon.

Penumbra Part of the shadow within which the light source is only partially obscured. In the context of this book it means the outer part of the Moon’s shadow.

Perigee The point in the orbit of the Moon that is closest to the Earth.

Perihelion The point in the orbit of the Earth that is closest to the Sun.

Prominence A massive gaseous formation above the surface of the Sun, which can be seen during a total eclipse.

Saros The eclipse cycle with a period of 223 synodic months or 6,585.32 days. After this time the Sun, Moon and Earth return to almost exactly the same relative positions.

Second Contact The beginning of the total phase of a solar eclipse. Starts when the leading edge of the Moon first completely obscures the Sun.

Solar Eclipse The passage of the new Moon between the Sun and the Earth in which the Moon’s shadow is cast over the Earth.

Spectroscope An optical instrument that spreads light out into its individual wavelengths, which can then be measured.

Synodic Month The period of time from one full Moon to the next full Moon.

Third Contact The end of a total phase of a solar eclipse. The trailing edge of the Moon first uncovers the Sun.

Totality The period during the solar eclipse when the Sun is completely obscured by the Moon.

Umbra That part of a shadow in which the source of the light is completely hidden from the observer. In the context of this book it means the Moon’s shadow.

Zodiac A band on the celestial sphere either side of the ecliptic divided into twelve equal parts of 30° each. Each part contains a specific constellation used to identify celestial objects moving along the ecliptic.