An Orbital Inclination is the angle between the plane of an
orbit and a reference plane. For example, the orbital inclination
of an Earth satellite might be given using the plane of
the Earth's equator as a reference, or the plane of the
Moon's orbit. The inclination of a planet's orbit is often
given using the Ecliptic as a reference.
The term is used for Binary Stars and Extra Solar Planets using the
plane of reference to be a plane perpendicular to the line-of-sight
- The Moon's orbit can be described by an inclination as compared to the plane of Earth's equator (the ecliptic, 5.14deg).
- The Earth's orbit can be described by an inclination as compared to the Sun's equator (7.155deg).
- A Transiting Planet (exoplanet) has an orbital inclination close to 90deg.