粗调光路共轴：开始时不要从望远镜内部观察，应先从望远镜的上面，通过准星和缺口观察光杠杆的平面镜里是否有标尺的像。若没有，可通过调节望远镜焦距而使像最终出现在平面镜内。Coaxiality of the light path: do not observe from the inside of the telescope at first, but observe whether there is a ruler image in the plane mirror of the optical lever from the top of the telescope through the collimation and notch. If not, the image can finally appear in the plane mirror by adjusting the focal length of the telescope.