Moon Phases - MoonPhase
MoonPhase draws tonight's moon as it actually looks, with the lit fraction, the moon's age in days and the phase name, and counts down to the next full and new moon. For the city you choose it also lists moonrise and moonset, sunrise and sunset, and the golden and blue hours that photographers plan around.
Everything is computed from astronomical formulas based on Jean Meeus's well-known algorithms, so the page needs no data feed once it has loaded. That makes it useful for planning a night photo, a fishing or garden calendar, a stargazing trip that needs a dark sky, or simply answering 'is that a waxing or waning moon?'.
It runs in your browser with no account. Saved places and display settings stay in this browser.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use Moon Phases
- Set your location. Open Settings and tap the location card. Search for a city and pick it from the results, or tap Use Current Location and allow location access. The page starts with Tokyo until you choose a place.
- Read today's moon. The Moon tab shows the rendered moon, phase name, illumination and moon age, then moonrise and moonset, sunrise and sunset, and how many days remain until the next full and new moon.
- Move between days. Use the arrows beside the date to step backwards or forwards one day at a time.
- Open the details. Tap the moon for Moon Details: the moon's current altitude and azimuth, whether it is above the horizon, its distance from Earth, and the golden hour and blue hour times for the day.
- Browse the calendar. The Calendar tab shows a small moon icon for every day of the month. Use the arrows to change month, and tap a day to open it on the Moon tab.
- Adjust display settings. In Settings, choose 24-hour time and kilometres or miles for distance.
Features
- Moon rendered by phase with illumination percentage and moon age
- Phase names from New Moon to Waning Crescent
- Days until the next full moon and new moon
- Moonrise, moonset, sunrise and sunset for your location
- Golden hour and blue hour times
- Moon altitude, azimuth and distance
- Monthly moon calendar
- City search and saved locations
- Calculated locally with Meeus astronomical algorithms
Understanding the phases of the Moon
Why the Moon has phases
The Moon has no light of its own. Half of it is always lit by the Sun, and the phase is simply how much of that lit half faces us as the Moon orbits Earth. At new moon it sits roughly between Earth and the Sun, so the lit side faces away. At full moon it is on the opposite side of Earth from the Sun and we see the whole lit face.
One full cycle, called a synodic month, averages about 29.5 days. The moon age shown in the app is the number of days since the last new moon.
The eight named phases
After new moon comes a waxing crescent, a thin sliver in the evening sky after sunset. First quarter, about a week later, shows a half-lit disc high in the evening. The waxing gibbous phase grows toward full moon, which rises around sunset and stays up all night. Then the cycle reverses: waning gibbous, last quarter (half lit, rising around midnight) and waning crescent, seen before dawn. 'Waxing' means growing and 'waning' means shrinking.
Moonrise and moonset
On average the Moon rises about 50 minutes later each day, though the daily delay varies with the season and your latitude. That is why a full moon rises near sunset, a last-quarter moon rises around midnight and a new moon rises and sets with the Sun, which makes it invisible. On some days at certain latitudes there is no moonrise or no moonset at all.
Golden hour and blue hour
The golden hour is the period shortly after sunrise and before sunset when the Sun is low, giving warm, soft, directional light. The blue hour comes when the Sun is just below the horizon, roughly between 4 and 6 degrees down, and the sky turns deep blue. Both are popular with photographers, and the exact times shift with date and latitude.
For seeing faint stars and the Milky Way, the best nights are around new moon, when moonlight doesn't brighten the sky.
Frequently asked questions
Does it need an internet connection?
The calculations happen in your browser. A connection is only needed to load the page and to search for a city.
Where are my places and settings stored?
Only in this browser on this device. There is no account. Clearing site data or switching browsers resets them.
How accurate is it?
The phase, illumination and Sun times come from standard astronomical formulas and are suitable for planning. Times can differ by a few minutes from official almanacs because of terrain, elevation and atmospheric conditions.
Can it remind me before a full moon?
Not on the web, because a web page can't send notifications after it is closed. The iPhone and Android apps offer full moon, new moon and moonrise notifications.
What is different from the phone app?
The apps add notifications and show ads that a subscription removes. The web version has no ads, purchases or notifications.
Limitations of the web version
- No notifications
- City search needs an internet connection
- Your current location is saved by coordinates rather than a place name
- Saved places stay in one browser and don't sync
Phone app
Moon Phases is also available as an app for phones and tablets: