(1) The horizontal axis of the collimation part shall be perpendicular to the vertical axis. During the inspection, the instrument shall be roughly leveled, the collimation part shall be rotated to make its level tube parallel to the connecting line of any two foot screws, the foot screw shall be adjusted to center the bubble, and then the collimation part shall be rotated 180 degrees. If the bubble is still centered, it shall be said that the conditions are met, otherwise it shall be corrected.
The purpose of correction is to make the axis of the leveling tube perpendicular to the vertical axis, that is, use the correction needle to move the correction screw at one end of the leveling tube to make the bubble return half to the middle position. In order to make the vertical axis vertical, use the foot screw to center the bubble. This inspection and correction must be repeated until the conditions are met.
(2) Inspection and correction that the vertical cross wire shall be perpendicular to the horizontal axis
During the inspection, aim a clear small point with the vertical wire of the cross wire to make the telescope rotate up and down around the horizontal axis. If the small point always moves on the vertical wire, the conditions are met, otherwise it needs to be corrected.
During calibration, loosen the four compression ring screws (the eyepiece equipped with cross wire ring is connected with the telescope barrel with compression ring and four compression ring screws. Rotate the eyepiece barrel to make the small point always move on the cross wire vertical wire. After calibration, tighten the compression ring screws.
(3) The collimation axis shall be perpendicular to the horizontal axis for inspection and correction. Select a target at a horizontal position, observe it from the left to the right, and take their readings (taking into account the constant of 180 degrees) to get twice the C (C = 1 / 2（ ɑ Left - ɑ Right).
(4) The horizontal axis shall be perpendicular to the vertical axis. For inspection and correction, the instrument shall be placed near the higher wall. Aim at a point P high on the wall at the left position of the disk (the elevation angle should be greater than 30 degrees), and lay down the telescope to set a point M1 on the wall. Turn the telescope upside down, aim at point P on the right, and then level the telescope to set another point M2 on the wall. If M1 coincides with m2, the conditions are met, otherwise correction is required. During correction, aim at the midpoint m of M1 and M2, fix the aiming part, and rotate the telescope upward. At this time, the intersection point of the crosshair will not be aligned with point P. Raise or lower one end of the horizontal axis so that the intersection of the crosshairs is aligned with the P point. This inspection shall also be repeated until the conditions are met. Among the above four inspections and corrections, one, three and four are the most important, and it is best to carry out them frequently during the observation period. After each inspection, the relevant correction screws must be tightened.