以下操作不正确的是Which operation below is incorrect

A、光栅是精密的光学元件，不允许用手或其它物体触及光栅表面The grating is a precise optical element. It is not allowed to touch the grating surface with hands or other objects;
B、测量过程中，不要碰动光栅，否则将破坏入射光与光栅平面的垂直During the measurement, do not touch the grating, otherwise the perpendicularity of incident light to grating plane will be destroyed;
C、以光栅平面为反射面，用自准直法调节光栅平面与望远镜的光轴垂直，此时应分别调节望远镜和平台下的螺丝
A、B使得从望远镜中观察到的十字像（由光栅反射回来）与望远镜的十字叉丝重合（注意：此时衍射的零级像也与叉丝的竖线重合），然后固定载物台Taking the grating plane as the reflecting surface, the grating plane is adjusted to be perpendicular to the optical axis of the telescope by autocollimation method. At this time, the screws A and B under the telescope and the platform should be adjusted respectively so that the crisscross image observed from the telescope (reflected by the grating) coincides with the reticle of the telescope (Note: at this time, the zero order diffraction image also coincides with the vertical line of the crosshair). Subsequently, the stage should be fixed;
D、调节望远镜的轴垂直于仪器的转轴时可用“渐近法”，即调节平台下的螺丝，使绿色十字像的中心逼近分划板十字刻线的水平线的一半，再调节望远镜的倾角螺丝及平台下的螺丝，使绿色十字像与十字刻线重合，然后旋转载物台 ，重复上述步骤直到两个反射面反射回来的绿十字像都与分划板上的十字刻线重合，这时望远镜的光轴与分光计的转轴就垂直The "asymptotic method" can be used to adjust the axis of the telescope perpendicular to the rotating axis of the instrument, i.e, adjust the screw under the platform so that the center of the Green Crisscross image approaches half of the horizontal line of the reticle, and then adjust the tilt screw of the telescope and the screw under the platform to make the Green Crisscross image coincide with the cross mark of reticle. Rotate the stage and repeat the above steps until the Green Crisscross images reflected from the two reflecting surfaces coincide with the cross marks of the reticle. By now, the optical axis of the telescope is perpendicular to the rotation axis of the spectrometer