The moon has eight phases in each lunar cycle: four primary phases and four secondary phases. The four primary phases are:
- new moon
- first quarter
- full moon
- third quarter
These occur at a specific time each month, and you can check the exact time to see if the moon will be risen and visible in your location as it reaches that phase.
The four secondary phases are not at a specific time; they are transitions that the moon goes through between the primary phases. The moon may stay in one of these phases for seven days. They are:
- waxing crescent
- waxing gibbous
- waning gibbous
- waning crescent
For the most part, the names of the moon phases make sense, such as “waxing” when the illuminated part of the moon is growing and “waning” when the illuminated part is shrinking. The “crescent” moon is also a familiar concept, as the moon appears in the shape of a crescent during this time. Perhaps the most novel term in the lunar calendar is “gibbous,” which broadly means convex, but in astronomy specifically refers to the time when the moon is more than half but not wholly illuminated.
Let’s look at an entire lunar cycle.