drawtube meaning in Chinese

活镜筒
显微镜抽筒

Finally , inside this reflection of the secondary , you can see the focuser drawtube and your eye
最后，在副镜的反射像中，你能看到调焦座的伸缩管和你的眼睛的像。
Like the primary mirror , the eyepiece has an optical axis , and this axis should be aimed at the center of the main mirror for best performance ? though in practice it is the center axis of the focuser drawtube that you aim at the primary mirror
目镜和主镜一样也有光轴，光轴应该对准主镜的中心? ?尽管实际上，目镜的光轴对准的是调焦筒（相当于调焦座）的中心。