In the arch, a star is flashing, just like a lamp in Nightcrawler.
There is an intellectual error in this poem. Because the meniscus (waning moon) appears in a vertical state, that is to say, the meniscus should be upturned, and the gap of the meniscus is not really missing anything, but the sunlight is not shining and it is opaque. Because the moon is a sphere, it is round at any time, not curved, so there are no stars in the "arch". The stars should appear on one side of the arc, that is, outside the "arch"
Moon phase, astronomical terminology. Moon phase is the name in astronomy, which refers to the part of the moon illuminated by the sun seen on the earth. As the moon moves a long distance from west to east in the starry sky every day, its shape is constantly changing, which is the phase change of the moon, called the moon phase.
1. On the first day of the lunar month, the moon lies between the sun and the earth. People on the earth see the dark side of the moon that deviates from the sun, so they can't see the moon on the earth, which is called a new moon or a new moon. See position a in figure 1 for its visual shape. This moon phase almost rises and sets with the sun, that is, it rises in the morning and sets at dusk, and its existence can only be detected during the solar eclipse.
2. After the new moon, the moon rotates eastward around the earth, leaving the middle between the earth and the sun and leaning to one side, that is, the moon is located in the east of the sun. The half moon illuminated by the sun faces west. On the earth, we can see that part of it is sickle-shaped, and its convex surface faces the western sun. This is the so-called moth eyebrow moon. See position b in figure 1 for its visual shape. The moon rises after sunrise and sets after sunset. It is in the sky with the sun, in the bright sky, so we can't see the moon phase. Only after sunset can you see the moth-eyebrow moon in the western sky.
On the seventh and eighth day of the lunar calendar, as the moon continues to move eastward around the earth, the relative positions of the sun, the earth and the moon become right angles, that is, the connection between the moon and the earth is 90 degrees. Observers on earth only see the bright half of the moon in the west. The bright side faces west for a month and a half, which is called the first quarter moon. See position c in figure 1 for its visual shape. The first quarter moon comes out around noon and appears in the southern sky at dusk. Assume that the observer is located in the mid-latitude of the northern hemisphere, falls below the horizon from the west at midnight, and is visible in the first half of the night.
4. On the 1 1 day and 12 day of each lunar month, observers on the earth see that more than half of the western part of the moon is illuminated by the sun, and the moon phase becomes a convex moon. See position d in figure 1 for its visual shape. The convex moon comes out after noon, in the southeast sky at dusk, the moon faces west, then continues to the west, and falls from the western horizon before dawn, and can be seen at midnight.
On the fifteenth and sixteenth day of the first lunar month, the moon moves to the outside of the earth, that is, the sun and the moon are located on both sides of the earth. Because there is an included angle θ between the ecliptic plane and the ecliptic plane (the average value of θ is 5 09'), under normal circumstances, the earth can't block sunlight, and the whole bright side of the moon faces the earth, so people see a full moon, which is called the full moon or the moon. See position e in figure 1 for its visual shape. The full moon rises from the eastern horizon at night, reaches the top of the head at midnight, that is, the southern sky, and sets in the west in the morning, and the moon can be seen all night.
6. In a few days, on18th and19th of each month in the lunar calendar, the moon phase will turn into a convex moon and the moon will face east. See position f in figure 1 for its visual shape. At this time, the convex moon comes out after dusk, sets before noon, and is visible most of the night.
7. On the 22nd and 23rd of each month in the lunar calendar, the relative positions of the sun, the earth and the moon become right angles again, and the moon is 90 degrees west of the connecting line between the sun and the earth. At this time, we see that the eastern half of the moon is bright, which is the half moon facing east, called the last quarter moon. See position g in figure 1 for its apparent shape. It rises from the eastern horizon at midnight, hangs high in the southern sky at dawn and sunrise, sets from the western horizon at noon, and is visible at midnight.
8. In a few days, on the 25th and 26th of each month in the lunar calendar, the moon phase will turn into a broken moon, with its bright face facing east. See position h in figure 1 for its visual shape. At this time, the moon rises after midnight, sets before dusk and is visible before dawn.
The moon then continued to move eastward, and then moved between the sun and the earth, that is, point A, and the moon changed phase. It can be seen that the change of the moon phase is the new moon (the first day) → the moth-eyebrow moon → the first quarter moon (the seventh and eighth day) → the convex moon → the full moon (the fifteenth and sixteenth day) → the convex moon → the second quarter moon (the twenty-second and twenty-third day) → the waning moon → the new moon. The moon goes from point A to point B → point C → point D → point E → point F → point G → point H, and the time interval between the new moon and the next new moon is called Shuowangyue.
I hope it can help you solve the problem.