AN INFORMATIONAL GUIDE: LUNAR CALENDAR LORE
The word month takes its root from the Moon.
Here LCL stands for lunar calendar lore: this is an independent informational guide, not an organisation. It explains the 29.5-day cycle of phases, the old names given to each full moon, and why the calendar and the Moon drift apart.
LOOK UP 29.5 days
THE SHORT ANSWER
Royal Museums Greenwich: at almost all times,
half of the Moon is lit by the Sun.
WHY PHASES
Phases come from the positions of the Moon, Sun and Earth. Between us and the Sun it is new; on the far side of Earth it is full.
Name this moonWHY ONE FACE
The Moon rotates at the same speed it orbits Earth, NASA explains, so the same side always faces us.
See the numbersWHY NAMES
Many familiar names reached us from Native American timekeeping, later adopted by colonial Americans and popular culture.
Go moon watchingNAME THIS MOON
Pick a month. The bar shows how widely the most popular name is used, going by the Royal Museums Greenwich guide.
Names follow the Royal Museums Greenwich guide to full moon names. Different cultures and tribes use different names; these are the most popular in English today.
TWO NUMBERS WORTH KNOWING
The gap between them is why
full moon dates drift through the calendar.
29.5
Days for a full cycle of phases
That is not the same as the time the Moon takes to orbit Earth, which Royal Museums Greenwich gives as 27.3 days.
PHASES · RMG
11
Days short of a calendar year
Twelve cycles of phases take about 354 days, so every two and a half years or so an extra, 13th full moon fits into the year.
THE GAP · RMG
That extra full moon is one meaning of blue moon. The term once named the third full moon of a season with four, and is now also used for a second full moon in one month.
FOUR TIPS FROM NASA
These tips follow NASA's moon viewing guide.
For craters and mountains, try phases other than full. Shadows are stronger and make features easier to pick out.
Look along the terminator, the line between light and dark, where features cast long shadows.
The grey patches, the maria, are old solidified lava flows. The lighter highlands show the Moon's earliest crust.
Near a crescent at dusk or dawn, the dark part can glow faintly with sunlight reflected off Earth.
MONTH AND MOON
Royal Museums Greenwich notes that a month was originally 29 or 30 days, close to the lunar cycle. Some calendar months were later given extra days so that twelve months make up a 365-day solar year.
That is why the old names sit loosely on the modern calendar: a named full moon can fall early or late in its month, and some years hold thirteen.
Questions
Lunar calendar lore. This is an independent informational guide, not an organisation or observatory.
Eight named phases: new, waxing crescent, first quarter, waxing gibbous, full, waning gibbous, last quarter and waning crescent.
Many came from Native American timekeeping and were adopted by colonial Americans. Names vary between cultures and tribes.
The nearest full moon to the autumnal equinox, usually in September. Its light was said to let farmers work late.
One face, because it is tidally locked. A wobble called libration lets experienced observers see about 59 percent over time, NASA says.
The full, quarter and new moons are instants: the moments when the Moon is exactly fully, half or not at all lit as seen from Earth. Royal Museums Greenwich says the crescent and gibbous phases in between each last approximately a week.
NASA says that, if your eyesight is sharp enough and you give your eyes time to adjust, you may pick out some of the larger impact craters, including Copernicus, Kepler, Aristarchus and Tycho, and even the bright ray streaks around Copernicus or Tycho. For binoculars it suggests a magnification of at least 7; 10 or 15 shows more detail but may need a tripod.
Sources
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