Glossary E

Eclipse: The passage of one celestial body into the shadow cast by another.

Ecliptic: The track along which the Sun appears to travel around the celestial sphere.

Elongation: The angle between the Sun and a planet or other Solar System, when viewed from Earth.

Equatorial Mounting: One that enables a telescope to be turned around two axes in order to follow the motion of a celestial object across the sky.

Equinox: An occasion when the Sun is vertically overhead at a planet’s equator and day and night have equal duration for the whole planet.

Extrasolar Planet (Exoplanet): A planet that revolves around a star other than the sun.