The inclination of the orbit of a planet is defined as the angle produced between the plane of the orbit of the planet and the orbit of Earth.
The inclination of orbits of natural satellites is measured relative to the rotational axis of the body they orbit.
The inclination of a binary star is defined as the angle between the orbital plane and the direction to the observer. Binary stars with inclination close to 90 degrees are often eclipsing.
See also: axial tilt
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