The Moon Dictionary

Measured in days. For example, a Full Moon typically has an age of approximately 14.7 days.

This occurs when the moon is at apogee (farthest from Earth), making it appear smaller than the sun in the sky.

Observers standing in the antumbra will see an Annular Eclipse (Ring of Fire).

When a Full Moon coincides with apogee, it is often called a “Micromoon” because it appears smaller and dimmer.

Known in astrology as the “North Node” or “Dragon’s Head.” Eclipses can only occur near the nodes.

Named because this was the time of year when beavers began to take shelter in their lodges for the winter.

It can also refer to a February with no Full Moon. It is the “invisible” counterpart to a Blue Moon.

The red color comes from Rayleigh scattering—sunlight filtering through Earth’s atmosphere and projecting sunset colors onto the lunar surface.

The “seasonal” definition refers to the third Full Moon in a season that has four Full Moons. The moon does not actually appear blue.

Named because this is the time of year when male deer (bucks) begin to grow their new velvet antlers.

Named for the settling in of winter cold. Also sometimes called the Long Night Moon.

These are the most common “photo ops” for astrophotographers. Technically, they share the same right ascension.

Known for its terraced walls. It is often cited as the textbook example of a lunar crater.

Often used when the Harvest Moon falls early in October, making the September moon the “Corn Moon.”

Famous examples include Tycho (with its visible rays) and Copernicus.

Often used interchangeably with “New Moon,” though some traditions distinguish the Dark Moon as the day *before* the New Moon.

There is no permanent “dark side.” All sides of the moon receive sunlight. It is only “dark” in the sense that it is unknown or hidden from Earth’s view.

Known in astrology as the “South Node” or “Dragon’s Tail.”

Also known as the “Da Vinci Glow.” It allows you to see the outline of the full sphere even when only a crescent is lit.

There are usually two eclipse seasons per year.

The Moon’s orbit is tilted about 5 degrees relative to the ecliptic, which is why we don’t have eclipses every month.

Used in the calculation of the date of Easter.

First photographed by the Soviet Luna 3 probe in 1959. It is more heavily cratered than the near side and has fewer maria (seas).

It rises around noon and sets around midnight. It is called “First Quarter” because the moon has traveled 1/4 of its orbit.

Named for the abundance of wildflowers blooming during this month in the Northern Hemisphere.

The moon is 180 degrees opposite the sun. It rises at sunset and sets at sunrise.

The Metonic Cycle is a 19-year period after which the lunar phases recur on the same days of the year.

Famous for rising shortly after sunset for several days in a row, giving farmers extra light to harvest crops.

Its sighting is crucial in the Islamic Calendar for determining the start of months like Ramadan and Shawwal.

Named because historical hunters used the bright moonlight to track game preparing for winter.

Due to libration, we can see about 59% of the lunar surface over time, rather than just 50%.

Can only happen during a Full Moon. A total lunar eclipse results in a “Blood Moon.”

While scientifically debunked, the “Lunar Effect” remains a popular cultural myth regarding ER visits and crime rates.

Also known as a Synodic Month, lasting approximately 29.53 days.

Early astronomers mistook them for seas, hence the name “Mare” (Latin for sea).

This cycle is the mathematical basis for the Greek, Hebrew, and Babylonian calendars.

It appears about 14% smaller than a Supermoon.

Folklore says a moon halo predicts rain or snow coming soon.

It is not actually larger; it is a trick of the brain comparing the moon to foreground objects.

They are much fainter than solar rainbows and often appear white to the human eye due to low light, though long-exposure cameras reveal their colors.

This is the best time for stargazing as there is no moonlight pollution.

Occultations are used by astronomers to refine the moon’s exact orbit and map the terrain of its edge (limb).

It is the only lunar “Oceanus” (all others are Seas/Maria) and was the landing site of Apollo 12.

It looks like a “bite” has been taken out of the moon.

In a Penumbral Lunar Eclipse, the moon dims slightly but does not turn red or disappear.

A Full Moon at perigee is called a “Supermoon.”

It is NOT pink in color. Named after the pink phlox wildflowers that bloom in early spring.

These rays are composed of “ejecta” (debris) thrown out during the impact. The rays of Crater Tycho are visible with binoculars.

Essentially, “Moon Dust.” It is sharp and abrasive because there is no wind or water erosion to smooth the particles.

Eclipses separated by a Saros cycle have very similar geometry.

It is distinctively slightly blueish compared to other maria due to high titanium content in the basalt rock.

The lunar equivalent of geography.

Shorter than the Synodic Month (phase cycle).

Named for the heavy snowfalls typically seen in this month in North America.

Can only happen during a New Moon. It can be Total, Partial, or Annular.

Named by Algonquin tribes for the short strawberry harvesting season in the North.

Named because the giant sturgeon of the Great Lakes were most readily caught during this part of summer.

It appears brighter and larger than average. The technical term is “Perigee-Syzygy.”

Average length is 29.53 days. This is the basis for most lunar calendars.

Syzygy causes extreme “Spring Tides” in the oceans.

This is the best place to look with a telescope, as the shadows highlight the height of craters and mountains.

From the Latin for “lands.” They are older and more cratered than the dark Maria.

Also called “Last Quarter.” It rises around midnight and sets around noon.

This is why the Moon always shows the same face to Earth.

Total Solar Eclipses reveal the Sun’s corona.

Photographers often plan to capture the “ISS Transit,” where the Space Station appears as a silhouette against the Full Moon.

The “rays” (splash marks) from Tycho stretch across much of the visible face, making it look like the navel of the moon during a Full Moon.

To see a Total Solar Eclipse, you must be standing in the moon’s umbra.

Illuminated on the left side (Northern Hemisphere).

The illuminated portion is shrinking (waning) but still more than 50%.

Illuminated on the right side (Northern Hemisphere).

The moon appears to be “humpbacked” and growing larger each night.

Associated with the howling of hungry wolves outside villages in deep winter.

Named for the earthworms that appear as the soil thaws, signaling the return of robins.

The moon rarely hits the exact zenith unless you are in the tropics, but it is a key reference point for describing the moon’s position.

While not lunar, it is often confused with moonlight or twilight and is best seen during the New Moon (dark skies).