What algorithm is used for moon calculations?

This tool uses a simplified browser-side implementation based on lunar terms described in "Astronomical Algorithms" by Jean Meeus. It is intended for planning, not as a certified ephemeris. Compare critical observations with the U.S. Naval Observatory or another authoritative almanac.

Why does moonrise shift by about 50 minutes each day?

The Moon orbits Earth eastward, completing one orbit in about 29.5 days. Each day the Moon moves roughly 13° eastward relative to the stars, so the Earth must rotate an extra ~50 minutes to bring the Moon back to the same altitude. This is why moonrise times are not fixed like solar times.

What does moon age mean?

Moon age is the number of days since the last new moon. A value of 0 means new moon, ~7 days is first quarter, ~14–15 days is full moon, and ~22 days is last quarter. The full lunar cycle (synodic month) averages 29.53 days.

What is the illuminated fraction?

The illuminated fraction is the percentage of the Moon's visible disk that is lit by the Sun. At new moon it is 0%, at full moon it is 100%, and at the quarters it is approximately 50%. The value is derived from the phase angle between the Moon, Earth, and Sun.

Why might moonrise or moonset show "None" for my location?

Near the poles, the Moon can remain above or below the horizon for multiple days, similar to the midnight sun phenomenon for the Sun. When the Moon does not rise or set on a given date at your latitude, the calculator reports "None" with an explanation.

How accurate are the times shown?

These are planning estimates from a browser-side low-precision ephemeris and a standard refraction model. Local terrain, elevation, weather, atmospheric refraction and an incorrect UTC or daylight-saving offset can shift the observed time. Verify critical observations with an authoritative observatory or almanac.

Moonrise Moonset Calculator

Estimate moonrise, moonset and transit for a selected local date, coordinates and UTC offset, with a seven-day table, phase and illumination.

Location & Date

Latitude (°)

Longitude (°)

Date

UTC Offset (hours)

Coordinates and calculations stay in your browser. “Use My Location” asks for browser permission. The UTC offset is fixed; adjust it manually for the selected location and daylight-saving date.

Enter location and date to calculate moon times

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Lunar Phase

Illumination —

Moon Age —

Moonrise

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Transit

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Moonset

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Lunar Details

Right Ascension —

Declination —

Distance —

Phase Angle —

Above horizon at local noon —

Next Full Moon —

Seven-day local outlook

Date	Rise	Transit	Set	Illum.

Times use the fixed UTC offset entered above; daylight-saving transitions inside the seven-day range are not adjusted automatically. Events assume a level, unobstructed sea-level horizon and standard refraction.

Method and verification

Moonrise and moonset mean the apparent upper limb crossing an ideal horizon. Terrain, elevation and atmospheric conditions can change what you observe. For critical or legal use, verify the result with the U.S. Naval Observatory one-day service and read its rise/set definitions.

Summary

Estimate moonrise, moonset and transit for a selected local date, coordinates and UTC offset, with a seven-day table, phase and illumination.

How it works

Enter your latitude and longitude, or click "Use My Location" to auto-fill from your browser.
Select the date you want to evaluate and enter your UTC offset.
The tool computes the Julian Day Number for the given date.
Lunar position (right ascension and declination) is calculated using Meeus low-precision orbital elements.
Rise and set use the standard apparent upper-limb criterion: horizontal parallax, lunar semidiameter and 34 arcminutes of refraction.
The lunar phase angle and illuminated fraction are derived from the Moon's elongation from the Sun.

Use cases

Plan astrophotography sessions around a new moon for dark skies.
Find moonrise times for landscape photography with a full moon backdrop.
Schedule nighttime hiking or camping trips with adequate moonlight.
Track the lunar cycle for fishing, gardening, or tidal predictions.
Determine moon visibility for astronomical observations.
Calculate moon age and phase for religious or cultural calendar purposes.
Verify moonrise azimuth for alignment photography at specific landmarks.
Plan wildlife observation activities that depend on moon brightness.

Frequently Asked Questions

Last updated: 2026-09-20 · Reviewed by Nham Vu