This paper describes the principle of computing map magnetic declinations, a new method of computing MMD is presented.
详细论述了磁偏角自动计算的原理，并提出了一种利用地磁图自动计算图幅磁偏角的新方法。
2
The errors of the circle of a meridian circle will immediately affect the precision in determining celestial bodies' declinations.
刻度盘的误差，是子午环固有的仪器误差之一，它直接影响了天体赤纬的测定精度。
3
The relation between the error of nutation constant and the corrections of declinations, proper motions calculated by chain method is analysed, and the method to correct this effect is considered.