Bresser T-ring with M42 thread allows you to attach Nikon SLRs cameras to telescopes via T-thread focusing devices for shooting at prime focus. It can also be used in conjunction with a T-adapter to mount the camera on any telescope with a 1.25" or 2" focuser. The T-ring on one side is fixed to the bayonet mount of the camera body, and on the other – to the telescope focuser or T-shaped adapter.