Zoom lens

It,s used for Astronomical telescope . The whole is composed of 3parts: 1. Adapter ring : use 60611 alumina processing, the surface chromium-plated and the inside diameter use matt process. 2.Pre-lans barrel : use 6061 alumina procesing , anodic oxidation threatment of the surface the inside diameteralso use matt process. 3.Middle-lens barrel : USE 6061 Alumina processing , the multi-startthead is used to focusing a lens . After assembly , Pre-less barrel and Middle-lens barrel can free backwards or forwards in regulating . It,s one of high precesion regulation equipment.