Weizi yueliang daquan

According to the longitude difference between the sun and the moon, the moon can be divided into eight types (see below), among which there are four main types: new moon, first quarter moon, full moon and last quarter moon.

1. new moon (new moon on the first day)

As shown in position A in figure 1, there is no reflection of the sun light near the ground, so the moon can hardly be seen. The new moon rises in the morning and sets at dusk.

2. Emei month (from the second day to the seventh day of the lunar calendar)

The moon revolves around the earth and reaches position B as shown in figure 1. The earth can see the illuminated part of the moon, which is sickle-shaped and faces the western sun. The Emei moon works at sunrise and stops at sunset. Therefore, it will take some time after sunset to see the Emei moon in the western sky.

3. The first quarter of the moon (the eighth day of the eighth lunar month is Cheng)

As shown in position c in figure 1, the relative positions of the sun, the earth and the moon are at right angles of 90 degrees, so it is observed that the moon is brighter in the western half. The moon rises in the first quarter and appears in the southern sky at dusk. Assuming that the observer is located in the mid-latitude of the northern hemisphere, the moon can be observed setting on the western horizon at midnight. Visible at midnight.

The full moon rises gradually (from the ninth day of the ninth lunar month to the fourteenth lunar month)

As shown in position D in figure 1, at this time, the moon is mostly bright to the west, and the convex moon appears after noon, in the southeast sky after dusk, and sets from the western horizon before dawn, and is visible most of the night.

5. Full moon (the fifteenth day of the lunar calendar means "looking" and the sixteenth day means "looking")

As shown in position E in figure 1, at this time, the sun and the moon are located on both sides of the earth. Because there is an angle between the ecliptic plane and the ecliptic plane (about 5 degrees Z on average), in most cases, the earth can't stop the sunlight, so the bright moon is facing the earth, and people can see a bright moon. When the sun sets at night, the full moon rises from the eastern horizon, lies in the southern sky at midnight and sets on the western horizon in the morning. Visible all night.

6. Monthly deficit (from lunar calendar1July to 23)

As shown in figure 1, the middle position of f, at this time, most of the moon is bright in the east. Because of the different relative positions, it is a small part of the upper part that gradually loses the convex moon, which is contrary to the gradually surplus convex moon. The waning moon rises after dusk, sets before noon and can be seen most of the night.

7. First quarter moon (23rd lunar month)

As shown in position G in figure 1, the relative positions of the sun, the earth and the moon are at right angles again, and the moon seen at this time is bright in the east. The last quarter moon rises at midnight, hangs in the southern sky at sunrise, sets from the western horizon at noon and is visible at midnight.

8. The waning moon (the 24th to 30th day of the lunar calendar is "unlucky")

As shown in position H in figure 1, the Emei moon faces east. Sunrise after midnight, sunset before dusk, visible before dawn.