Moonrise Moment

Orbit glossary

What is libration?

Libration is the Moon's apparent nodding and rolling motion, which lets observers on Earth see slightly more than half of its surface over time.

Earth and the Moon shown at two points along an elliptical lunar orbit.
A visual guide to libration. Original Moonrise Moment illustration.

What it means

Libration describes part of the Moon's motion or position in space. The Moon follows a slightly elliptical, tilted orbit, so its distance, apparent path, rise time, and alignment with the Sun change continuously. These orbital relationships explain many patterns that observers notice from night to night.

Keep exploring

Orbit Apogee

The point in the Moon's orbit where it is farthest from Earth.

 Orbit Declination

A celestial coordinate comparable to latitude on Earth. It measures angular distance north or south of the celestial equator.

 Orbit Ecliptic

The Sun's apparent yearly path across Earth's sky. The Moon and planets remain near this path because their orbits have relatively small tilts.

 Orbit Equinox

Either of two yearly moments when the Sun crosses Earth's celestial equator and day and night are roughly equal in length.

Sources and further reading

This definition was written in plain language and checked against these science references.

Moonrise Moment showing the live direction and countdown screen.

See the Moon from where you stand.

Find the next moonrise, the direction to face, and the phase you will see from your location.

Join TestFlight