astrologia
Lunation
A lunation is the cycle between consecutive new Moons. It lasts about 29.5 days, distinct from the Moon’s revolution relative to the stars.
How it is defined
Phases change because the illuminated portion we see changes. Earth’s shadow does not cause ordinary phases; it is involved in lunar eclipses.
How to read it
To check the phenomenon, distinguish the calculated position, its reference time and what an observer can see from their location. These related details answer different questions.
A concrete example
At first quarter we see roughly half the near side illuminated. Quarter names a stage in the cycle, not 25% illumination.
Explore further
Explore the sources and related concepts. When consulting tables or calendars, look for the date, coordinates and reference frame they use.