Moonrise Moment

Observing glossary

What is refraction?

Refraction is the bending of light through Earth's atmosphere, which makes objects near the horizon appear slightly higher than their geometric positions.

The Moon above an ocean horizon with altitude and azimuth guide arcs.
A visual guide to refraction. Original Moonrise Moment illustration.

What it means

Refraction is part of the practical language of skywatching. It helps describe where the Moon appears, how it moves across a local sky, or what an observer actually sees. Because every horizon and viewing location is different, observing terms are most useful when paired with a specific place and time.

Keep exploring

Observing Altitude

The angle of an object above the observer's horizon, measured from 0 degrees at the horizon to 90 degrees at the zenith.

 Observing Azimuth

A compass direction measured clockwise around the horizon, usually from 0 degrees at north through 90 degrees at east.

 Observing Culmination

The moment a celestial object crosses the observer's meridian and usually reaches its highest altitude for that passage.

 Observing Earthshine

The faint glow on the Moon's unlit portion caused by sunlight reflecting from Earth to the Moon and back toward the observer.

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