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About the Moon Distance Calculator

The Moon Distance Calculator calculates the approximate time and distance from the Moon’s center to the Earth’s center, as well as the lunar perigee and apogee.

Illustration image
Difference in Moon's size at Perigee & Apogee
The Moon orbits around the Earth in an elliptical path

The Moon's orbit around the Earth is elliptical, with one side of the orbit closer to Earth than the other. These two extremes of the moon’s orbit are the lunar perigee and apogee. Although the moon may look the same at each full moon, there is quite a difference in its size throughout the year.

Any location available through the World Clock may be selected, and the calculator will adjust for local time. The local time is adjusted if the selected location observes daylight saving time during parts of the year.

Lunar Perigee

The lunar perigee occurs about once a month and around the time of the full moon from January to May and the new moon from July to December in 2011. This is when the moon is nearest to the Earth during its monthly orbit. During this time, the moon may appear brighter and larger in the sky.

Due to lunar libration, which is the slow rocking back and forth of the Moon that allows an observer to see slightly different halves of the moon’s surface at different times, the moon’s rotation is slower than its orbital motion at its perigee. This allows us to see up to eight degrees of longitude of its eastern (right) far side.

When a full moon occurs during a lunar perigee, it may look larger than average. Compared to its apogee, the moon’s diameter looks about 12-14% larger at its perigee.

Lunar Apogee

The lunar apogee is the point farthest from the Earth during the moon’s monthly orbit. In 2011, it occurs around the time of the full moon from August to December and the new moon from January to May. When the Moon reaches its apogee, its rotation is faster than its orbital motion which reveals eight degrees of longitude of its western (left) far side.

How to view the Moon

The best time to look at the moon is when it is near the horizon due to atmospheric distortion. At this time, illusion mixes with reality to produce a low-hanging moon that looks unnaturally large when compared to foreground objects.

Photographing the moon can be tricky and while some photographers prefer to take a photo of the moonset because of the rich colors in the sky, the moon’s phase is also an important factor to consider in moon photography.

Photographing the full moon can be difficult because the moon can appear to be flat and very bright.  It is recommended that you use a SLR (Single Lens Reflex) camera with a long lens or a semi-professional digital camera, rather than a point-and-shoot or a single-use "disposable" camera. Other issues to consider are exposure times, film types, and lenses needed to take photographs of the moon.

Local Time Conversion

The moon distance calculator automatically takes into account daylight saving time at the selected location, except for UTC/GMT. To display the moon distances for a location within this timezone (e.g. London) please select the city - not UTC/GMT.

If you select a future year, the results may be wrong due to future changes in a country's daylight saving time rules. For years before the introduction of standard time zones, the calculator may display "local mean solar time", which is an average yearly value based on the moment when the sun passes a location's meridian. In reality, this moment may differ by up to 17 minutes from the average passing time.

Calculation Accuracy

The accuracy of the distances calculated should be within a few hundred miles or kilometers. The distance is measured from the Earth’s center to the Moon’s center.

The accuracy of the times calculated are approximate and are within the hour. All times are based on the user’s local time. The local time is adjusted if the selected location observes daylight saving time during parts of the year.

Topics: Help

In this Article

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All about the Moon

  1. Phases of the Moon
  2. Full Moon names
  3. The Moon's orbit
  4. Is a blue Moon blue?
  5. What is a supermoon?
  6. Micro Moon versus supermoon
  7. Moonbows
  8. Black Moon
  9. Moon Phases - definitions

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