This adapter is mainly used for direct focus photography with SLR cameras, particularly suitable for Newton reflected telescope, Do not take a light pathdo not occupation the optical path, one size of the adapter connect to digital camera or other T2 accessories, the other size insert to 2" telescope focuser or other accessories. This adapter has a standard 48mm (M48 x 0.75 ) male thread on one side to connect to diagonal body and a standard 48mm (M48 x 0.75 ) female thread on the other side to accept 2" astronomy filters.