The starry sky in autumn is wonderful! Here comes the observation guide.

On September 4th, the eastern distance of Mercury. Mercury is the closest planet to the sun and the most difficult planet to observe. Most of the year is lost in the sunshine, which we can't see on the ground. Only when mercury moves to the maximum angle with the sun can we barely see it at the eastern low altitude before sunrise or at the western low altitude after sunset. In a year, the east distance and the west distance will appear three or four times each, but at sunset or sunrise, the horizon height of Mercury is different, and the observation conditions are different, both good and bad, and sometimes it is too low to be suitable for observation. This time, the east distance of Mercury was only 8 degrees at sunset in Beijing, and the observation conditions were extremely poor.

Entering September is even autumn in astronomy, and it gets dark earlier and earlier. After nightfall, the iconic constellation of summer still occupies the main position in the sky. Lyra, Aquila and Cygnus are near the zenith, and the summer triangle composed of Vega, Altair and Tianjin hangs overhead. But some representative constellations in autumn have risen from the eastern horizon.

The symbol of the starry sky in autumn is Pegasus quadrangle, which is located at the low altitude in the east at this time. It consists of four second-class stars. The three stars in the quadrilateral belong to Pegasus, representing the belly of Pegasus. The brightest star in the northeast corner of the quadrangle belongs to Andromeda, the brightest star in Andromeda. It forms Andromeda with several other bright stars in the north. Farther north of Andromeda is Perseus in the Milky Way. Above Perseus is Cassiopeia, also in the Milky Way. The five bright stars in Cassiopeia form the shape of the capital English letter "W", with the opening facing Polaris and spanning Polaris and the Big Dipper, which is very eye-catching. Above Cassiopeia is Cepheus, which is slightly darker. Together, these constellations are called "the royal family in the sky".

In the southern sky, due south is Sagittarius in the zodiac. Sagittarius is a large constellation. Although there are no first-class bright stars, there are two second-class stars and eight third-class stars, which are relatively concentrated in distribution and easy to identify. Sagittarius is in the Milky Way. This part of the Milky Way is the widest and brightest because the center of the Milky Way is Sagittarius.

To the west of Sagittarius is Scorpio, which is the main representative constellation of the summer night sky. The brightest star in Scorpio is red Mars. At this time, it is already low in the southwest after dark. In the Book of Songs, there is a poem "July is full of fire, and clothes are given in September", in which "July is full of fire" does not mean that the weather is hot, but describes the sky at this time. In July of the lunar calendar, Mars sets in the west and the weather begins to turn cold. In two months, the weather will get cold.

Mars, also called Antares, is the second star among the traditional 28 constellations in China. In order to observe the movements of the sun, the moon and the five planets, ancient Chinese astronomers divided the starry sky near the zodiac into twenty-eight star zones, called Twenty-eight Hostels, and divided these Twenty-eight Hostels into four groups, each with seven stars called Four Elephants, namely the Black Dragon in the East, Suzaku in the South, White Tiger in the West and Xuanwu in the North.

The Oriental Black Dragon corresponds to the starry sky from Virgo to Sagittarius, with the dragon head in Virgo and the dragon tail in Sagittarius. The head of this dragon in the sky rises from the ground after dark in spring, commonly known as "the dragon looks up". In summer night, the oriental black dragon appears completely in the southern sky, which is called "flying dragon in the sky" in the Book of Changes. In the autumn, the Black Dragon crossed the west for seven nights, and the Book of Changes called "Kang Long has regrets". Although the dragon's head has fallen off, its tail is still in the southern sky. The tail of Scorpio and skip of Sagittarius represent the tail of the black dragon.

The main bright star of Sagittarius in ancient China is divided into two stars, one of which belongs to the tail of the oriental black dragon and looks like a dustpan; One is Dousu, with six stars arranged in a bucket shape, which is commonly known as Nandou Six Stars in China. The six stars in Nandou have only one second-class star, and the brightness of other stars is only about 3, which is far less eye-catching than the Big Dipper. There is a saying in China mythology that "Beidou is the master of death and Nandou is the master of life". In ancient China, the winter solstice was near Dousu, so Dousu was always valued by astrologers.

Dousu is the first night of Xuanwu in the north of the Four Elephants, representing the snake head and body of Xuanwu. In ancient China, Xuanwu was imagined as a spiritual body composed of turtles and snakes, symbolizing longevity and wit. The seven nights in northern Xuanwu include seven stars: Dou, Niu, Nv, Xu, Wei, Shi and Bi, which are distributed in Sagittarius, Capricorn, Aquarius and Pegasus commonly used in the world from west to east. There are no particularly bright stars in the autumn night sky around here, which seems a bit bleak. But now bright Jupiter and Saturn are just in Capricorn, which adds a lot of color to this starry sky.

The only bright star in the autumn night sky has just risen from the southeast horizon. It is the brightest star in Pisces, and its Chinese name is Beiluoshimen, which means the gate of the military camp. The stars near Beiluoshimen are very dark, so this lonely bright star is even more prominent. It forms the shape of a fish with several dark stars in the west. In the south of Aquarius, the ancient Arabs called this star "fish mouth".

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