What Is a Half Moon Phase
A half moon refers to the first quarter and last quarter phases, when half of the Moon’s visible disk is illuminated. In astronomy, these are called quarter moons because the Moon has completed roughly one quarter of its orbit around Earth since the new moon.
When Do Half Moon Phases Occur
The first quarter moon appears roughly seven days after the new moon, while the last quarter moon appears about seven days before the next new moon. Each phase lasts for a moment in time, but the Moon appears similarly lit for several nights around that moment.
Why Half Moon Phases Matter
Half moon phases are useful for planning observations, because the Moon rises around noon and sets around midnight at first quarter, and rises around midnight and sets around noon at last quarter. This creates convenient evening or pre-dawn viewing windows. For more detailed lunar phase data, see https://timeanddate.com/moon/phases/
