Determination of the Irregularity of the Horizontal Axis with the Axis—Collimator

In this paper, the influence of the horizontal axis points drifting is described, which is caused by the irregularity of the axis and the difference betweent the temperatures of the two hands. The method is recounted for determining and correcting the error with the axis-collimator. Meantime, it is discussed how to determine the parameters of the axis-collimator. The estimate of the accuracy shows that when the electric-collimator and axis-collimator are used in the Low latitude Meridian Circle, the machining accracy of the axis and the stability of the axis system may be lower while the accuracy for the determination and correction of these errors is very high.