The sun appears to move in an arc across the sky.
太阳看起来在天空以弧线运行。
An early instrument for measuring altitude of celestial bodies, consisting of a90= graduated arc with a movable radius for measuring angles.
象限仪用来测量天体纬度的一种早期工具, 由一个有90度刻度的圆弧和一个用来测量角度的可移动的半径构成
