A point on the celestial sphere directly below the observer, diametrically opposite the zenith.
A point on the celestial sphere directly below the observer, diametrically opposite the zenith.
天底天球上，在观测者垂直向下的一点，与天顶完全相对
A point on the celestial sphere directly below the observer, diametrically opposite the zenith.
天底天球上，在观测者垂直向下的一点，与天顶完全相对