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Moon Applet


Month Date Year UT
date month year

Use the key "d" to increase the date, or shift key and "d" to decrease the date,
use the key "y" to increase the year, or shift key and "d" to decrease the year,

click into the applet first !

The planet name in brackets following the date is the ruler of the day.
The Golden Number of a year is its remainder after division by 19, plus 1.
 The epact is defined as the age of the moon on January 1 in days (since an "official" new moon),
which may be different from the "true" (astronomical) age of the moon.

How to compute the date of Easter by the epact.

Use the Data button to show the New Moon or Full Moon times and lunations for the year selected:

New Moon Dates

Full Moon dates

The mean error of the New Moon and Full Moon times for 2004 and 2005
compared to the times by USNO is less than 2 minutes.





Moon Data

Moon Phase

Moon Phases for a Year

Sun & Moon Polar Applet

Azimuth of the Sun and the Moon at rise or set

Longitude and orbit of the Moon

Illuminated Fraction, Rise and Set

Moon Distance


More details:

Blue Moon

Full Moon distance

Moon illuminated

Moon phase
          illuminated fraction


Diagram of time intervals between consecutive New Moons (duration of the lunation)
2004, January to 2025, September.

Moon synodic

The mean value of 269 lunations is 29.5295 days.

The mean value for a long time is 29.530589 days = 29 days 12 hours 44 minutes 03 seconds (synodic month).

Extreme lunations:

New Moon
Duration of the lunation
Moon, Earth
1973, Dec 24, 15:08 UT
to 1974, Jan 23, 11:04 UT
29 d 19 h 56 m = 29.8306 d
= 29 d 12 h 44 m + 7 h 12 m

Moon apogee Dec 25, Jan 28
Earth perihelion Jan 04

2035, Jun 06, 03:22 UT
to 2035, Jul 05, 10:02 UT
29 d 06 h 40 m = 29.2778 d
= 29 d 12 h 44 m - 6 h 04 m

Moon perigee Jun 06, Jul 04
Earth aphelion Jul 05

The variation is due to the excentricity of the Earth's orbit. The lunation will have its greatest possible duration when, at the instant of New Moon, the Moon is near its apogee and the Earth is near its perihelion. The shortest possible lunation will take place about six months earlier or later, when at New Moon the Moon is near perigee and the Earth near aphelion. There is a period 8.85 years.

A detailed discussion:
Jean Meeus: More mathematical Astronomy Morsels, Willman-Bell, 2002, ISBN 0-943396-74-3

lunation synodic
          period moon

distance earth

Earth-Moon and Sun-Earth distances

There is a periodicity of 19 years (Metonic Cycle):

19 tropical years = 19 * 365.24219 days = 6 939.602 days

235 lunations = 235 * 29.530589 days = 6 939.688 days

with an error of 0.086 days (2 h 4 min).

The 19-year cycle is also close (to somewhat more than half a day) to 255 draconic months, so it also is an eclipse cycle.

Diagram of time intervals between consecutive Full Moons (duration of the lunation)
2004, January to 2025, September (computed by Planet Applet)

full moon period

Diagram of time intervals between consecutive ascending node passages (draconic month)
for 2004, January to 2024, December (computed by
Planet Applet)

moon ascending

The mean value of 284 ascending node passages is 27.2133 days.

The Saros Cycle:

Synodic Month (New Moon to New Moon)

29.53059 days = 29d 12h 44m

Draconic Month (node to node)

27.21222 days = 27d 05h 06m

223 Synodic Months

223 * 29.53059 d = 6585.32 d ┼ 18 years 10 or 11 d 8 h

242 Draconic Months

242 * 27.21222 d = 6585.35 d ┼ 18 years 10 or 11 d 8 h

Any two eclipses separated by one Saros Cycle share very similar geometries.

Diagram of time intervals between consecutive perigees (anomalistic month)
for 2004, January to 2025, September (computed by
Planet Applet)

moon perigee
            anomalistic month

The mean duration of 284 anomalistic months is 27.555 days.

Perigee distances:

moon perigee

The mean perigee distance of 284 anomalistic months is 362562.4 km.

moon ecliptic

Ecliptic latitude of the Moon 2005 to 2007
the time axis is: Julian day - 2453000

altitude elevation

declination of the

elevation altitude full moon

Local transit elevation of subsequent Full Moons, Berlin, 2005-2007

The lowest-hanging full moon in 18 years: 2005, June 21

Summer Moon Illusion


A Blue Moon is the second full moon in a calendar month. Usually months have only one full moon, but occasionally a second one sneaks in. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average.


Distance of the Full Moon from the Earth

Web Links

Inconstant Moon (Fourmilab, John Walker)

Lunar Perigee and Apogee Calculator (Fourmilab, John Walker)

A Whale of a Full Moon (NASA Space Science News)

Astronomy Picture of the Day, December 22, 1999 (NASA)

Warum ist der Mond am Horizont so gro▀?

The Moon Illusion,An Unsolved Mystery.

Explaining the moon illusion

The Face of the Moon from Galileo to Apollo

The Church lunar calendar

Epact (Wikipedia)

What is the Epact?

Golden Number (Wikipedia)

Planetary Hours And Days

Last Modified: 2023, Oct 06