This focal reducer allows shorter exposures, by reducing the focal ratio of the telescope to half. This is especially useful for SCT and MCT owners, since this types of telescopes normally have a focal ratio above f/10. By reducing it to half, exposure duration is 4 times lower, and the field of view is 2 times larger. Refractor owners will also find it useful. However, Newtonian owners will not be able to achieve focus with it.