Great importance was attached to the constellations around the north celestial pole and those around the celestial equator. By using the north polar stars, which do not rise or set, they considered celestial objects in their relation to the Sun. They mentally positioned stars by imaginary lines through these stars to those that did rise and set.
Very early, the Chinese divided the sky into twenty-four lunar mansions, each regarded as the stars within its limits, in which the Moon happened to be at the time of interest.
In the late first century CE, Chang Hêng wrote that the heavens are spherical. Its circumference was divided into 365¼ units, each being the distance that the sun traveled in one day. An older school of thought stated that the heavens were extended endlessly.
