"Otsuki"、"Satsuki"with"Flat month"These three concepts have specific meanings in the lunar calendar and astronomy, and they are related to phenomena such as the phases of the moon, the full moon, and the eclipse of the moon. Here's an explanation of these three concepts:
OtsukiIn the lunar calendar, the big moon usually refers to the month of a moon cycle that lasts longer from full moon to full moon. That is, starting from a synodic month (the time from the new moon to the new moon), after 29 days, 12 hours, 44 minutes, and 3 seconds, if the full moon is late in time, it is called a great moon.
Because the lunar lunar moon phase cycle is not exactly equal to 295 days, but slightly different, so there will be a difference between the big month and the small month.
SatsukiCorresponding to the big moon, the small moon refers to the month in a lunar cycle in which the time from full moon to full moon is shorter. If the full moon is in a period of 29 days, 12 hours, 44 minutes, and 3 seconds, the time point of the full moon is earlier, it is called a small moon. This difference is due to the eccentricity of the moon's orbit, as well as the relative motion of the Earth and the moon.
Flat monthA mean moon is the time from one new moon to the next in a lunar cycle, i.e. 29 days, 12 hours, 44 minutes, and 3 seconds. This is an average because both the shape of the moon's orbit and the relative motion between the Earth and the moon cause the actual moon phase cycle to change.
These three concepts play a role in adjusting the length of the months in the lunar calendar, making the lunar calendar more in line with the actual moon phase phenomenon. In practical application, the months in the lunar calendar may be 29 or 30 days to accommodate changes in the phases of the moon.
This difference in the moon phase cycle also has a certain impact on the seasons of the year, agricultural activities, etc. In astronomy and the lunar calendar, accurate measurements and observations of these phenomena help to compile an accurate calendar.