Star of the foundation, is for continuous observation of astrology, knew all about the position of the stars.

The ancients through long-term observation, and gradually became united star distribution system, which is three walls, twenty BaSu system.

Three walls, namely pole-ziweiyuan, too city walls, walls, days of the fence "walls" mean.Three walls, namely three stars in the sky.Pole-ziweiyuan and day the name of the city walls, first appeared in "the Shi Shixing classics," too small walls in the name of the late.Pole-ziweiyuan including the region near the north celestial pole.Pole-ziweiyuan range including constellation virgo, backwardness, lion's part.Day the city walls, including the serpent, caption, serpent, part of the constellation skyhawk etc.

Day, month, five stars and meteors and comets and other celestial bodies, is movement in the sky.In order to have a precise description on their position, create a set of coordinate system, called 20 BaSu, also known as 28 stars shed or 28 "homes" is the meaning of stay, the historical records. The law book, said: "give up, day, month, the homes".Every night is a region, size is differ, included the number of stars are also different.Selected from every night a star as a standard of measuring object position, said the star to star.Night from under the stars and the night at the distance of the star drawing from the Angle of the celestial equator between said right ascension is poor, said the night at the equator is apart from the degree of.An object in a lodge from star east, and from the host star is less than the right ascension of difference between the host from degrees, is called the host, this difference is called the object of right ascension lodge, coupled with the Angle of the distance between the object and the arctic, say to the extreme.In this way, a degree of celestial bodies in the position of the stars by people shopping and go to extreme two Numbers can be identified.Twenty BaSu distribution near the celestial equator, from west to east, Japan, on the apparent motion of the same.They are seven nights: east Angle, port, rockwell, room, heart, tail, white;Northern seven nights: dou, cattle, female, empty, and room, wall;Western seven nights: kratos, Lou, stomach, the, bi, wishing, and;South seven nights: well, ghost, willow, star, zhang, wing, and more.Twenty BaSu every night at the distance of degree is not equal, the difference is bigger.Twenty BaSu system measuring, namely from each night at the distance of the star to east section measurement.Just like a train, from Beijing to tianjin, such as measuring the position of the train, measuring the distance from Beijing to train at the beginning.After the first leg, is from the first station to measure the distance to the train, and so on.Twenty BaSu distance of star is similar to the railway station along the way.

20 BaSu set, both the need of the calendar, also is the need of astrology.On the 20 BaSu is divided into four groups, according to the east seven nights as the black dragon, seven nights as basalt, north west seven nights for the white tiger, south seven lodge for the linnet.The four groups of stars is also called the four elephants or say four land.On the calendar, the four groups of astrology is the symbol of the four seasons.In astrology, the performance is a mysterious color.

Twenty BaSu system, is an important content of the ancient Chinese astronomy.The formation of it is not happen overnight.According to our speculation, it probably is the formation of star of need to give priority to, the needs of the calendar is complementary.Why do you say so?If it is based on the needs of the calendar is given priority to, use it to measure the sun in the sky location, then the lodge of the Angle should be equal, set up, is much more convenient.As Babylon the signs of the zodiac, is measuring the position of the sun on the ecliptic, the palace of the Angle is equal, convenient to use.But twenty BaSu each night at Angle of 45 to the biggest well night at 33 degrees, the smallest purple night at only 2 degrees, is not easy for you to apply.And each night at the distance of the star choice should with remarkable bright stars advisable, but in fact most of the night from the star is not the night at the brightest star.And 28 is apart from the star that is full of a Sunday, if the stars for a certain distance, can have another from star differ with its 180 degrees) (week by 360 degrees, if two pairs, as 14 pairs, each pair of 180 degrees, the most reasonable.But in fact from the star, the choice of a hash.So appear this kind of phenomenon, if think it is in the process of formation of lay particular stress on star, or some reason.

Twenty BaSu from start to finish, experience is a long time.In 1978, in hubei province with the county to discover one of the early years of the warring states tomb, there is a paint box cover, and there are twenty BaSu names and images of the blue dragon, white tiger.It can say, twenty BaSu originated from 5000 years ago, a few stars.Gradually add to the 5th century BC.