What is the exact value of the boundary range of the constellation dividing the sky area? What is the standard?

Different civilizations and historical periods may divide constellations differently. Most modern constellations evolved from the traditional constellations of ancient Greece, and the International Astronomical Union accurately divided the whole day into 88 constellations. The International Astronomical Union officially announced 88 constellations commonly used in the world. At the same time, it is based on the vernal equinox and equator of 1875. According to the different positions of the 88 constellations on the celestial sphere and the appearance of the stars, they are divided into five major regions, namely, the North Celestial Constellation (5), the Zodiac Constellation (12 constellation near the ecliptic on the celestial sphere), the Equator Constellation (10) and the South Celestial Constellation (-30 ~-90? 42), Polaris (40 ~ 90? , 19).

It seems that the movement of the constellation with the celestial sphere is caused by the movement of the earth itself, in which the rotation and revolution of the earth are the most obvious changes in the starry sky. Due to the rotation of the earth, the starry sky background rotates once a day around the celestial axis; The starry sky also changes slowly with the seasons. A year has passed, and the starry sky is almost the same as it was a year ago. The rotation axis of the earth's rotation also has a long-term motion, called precession, with a period of about 25,765 years.

This movement causes the periodic drift of the North Pole in the background of stars, which is called precession in astronomy. A cursory observation of the constellation in a short time can ignore this movement. In the northern hemisphere, the Polaris in Ursa minor is the most important basis for determining the direction in the starry sky. It can be seen from celestial coordinate system that the height of Polaris is consistent with the local latitude; But in fact, because the North Star is not bright, people usually use the Big Dipper to find the North Star, so as to determine the direction.

Put the spoon handle of Beidou (? Arrive? ) extend 5 times to find Polaris. In the case of low accuracy requirements, it can be considered that the direction of Polaris is the north. At low latitudes in the northern hemisphere, the Big Dipper will fall below the horizon, which can be based on the relative position and appearance of the Big Dipper. m？ (or? W? Cassiopeia to determine the position of the North Pole star. ?