The Moon
Phase, rise, set, distance and the illusions in between — what the Moon actually does, computed for a place and a date rather than described.
Moon
10 guides filed under this heading
- The eight moon phases are a labeling convention, not eight events
Half the Moon is lit at all times. What changes is the angle we see it from — and how eight names get attached to one continuous 29.53-day cycle.
4 min read - Why the Moon rises about fifty minutes later each night
The Moon gains roughly 50 minutes on the Sun every day — but the range is 20 minutes to over an hour, and the reason decides when a harvest moon happens.
3 min read - Waxing or waning: telling the two halves of the cycle apart
The lit side tells you which way the Moon is going — west means growing, east means shrinking — and the rule inverts south of the equator.
3 min read - Blue moon: what the term actually means, and why there are two definitions
A blue moon is either the second full moon in a month or the third in a season of four. Both are in use, they disagree, and neither involves color.
3 min read - Supermoon and micromoon: the 14% that the photographs do not show
A full moon near perigee is about 14% wider than one near apogee. Here are the 2026 dates, the definition behind the word, and what it does to tides.
3 min read - The Moon looks enormous at moonrise and it is not any bigger
The horizon Moon measures the same half a degree as the one overhead — slightly less, in fact. What changes is your brain's estimate of distance.
3 min read - Why the Moon is sometimes visible in daylight — and when to look
The Moon is up during the day for roughly half of every month. Which half, and at what hour, follows from phase and elongation, and it is predictable.
3 min read - The Moon is drifting away at 3.8 centimeters a year
Tidal friction is transferring Earth's spin to the Moon's orbit. Laser reflectors left by Apollo measure the drift, and the day is getting longer.
3 min read - The harvest moon: the one night a year when the Moon is on time
For several evenings around the September full moon, moonrise barely moves on the clock. At 45°N this year the delay is 18 to 23 minutes, not 50.
3 min read - The 18.6-year lunar standstill, measured rather than asserted
The Moon's declination range swings between ±18.5° and ±28.7° over 18.6 years. Here is the cycle, computed year by year, and why it is not a solstice.
3 min read
Reference pages
Tables and lookups on the same filing, answered without reading around it
- Moon phase on any date: illumination, age and the next four phases
Pick a date and the Moon's phase, the fraction of the disc that is lit, its age in days, its distance and the four principal phases that follow, all computed.
- Moonrise and moonset for sixteen cities, on any date
Moonrise and moonset for sixteen cities on any date, including the days with no rise at all — which happens far more often than most tables admit.
- Moon phases by month: the four principal instants
New moon, first quarter, full moon and last quarter for every month, dated and timed in UTC — the twelve months ahead, computed rather than copied.
Other topics on Meridian
Every guide on this site is filed under one of these
The Sun and the seasons
Day length, solar noon, twilight and the off-center clock: why the earliest sunset is not on the shortest day, and why the equinox is not twelve hours.
Eclipses and meteor showers
Shadow geometry and dust: which dates are real, where you have to stand, and the difference between a rate on paper and a rate in the sky.
The night sky
Constellations, precession, what your latitude hides from you, and how much of it light pollution has already taken.