This adapter ring allows you to attach a DSLR camera body to the viewing end of a standard telescope, turning the latter into a powerful telephoto lens!
The Moon is a good and bright target to practice for this aspect of astro photography. Use the LIVE view mode of your DSLR camera to achieve a sharp focus.
For beginners, this method may not be easy to master especially when shooting dim objects in the night sky, as long exposure on manual mode is required. In this case, a tracking mount is needed to counter the rotation of stars with respect to Earth.
*Picture is for reference only. T-rings of different camera brands will have different shapes.