This Vixen Optics Extender PH Kit for R200SS is a high-quality, made-in-Japan focal extender lens for serious astrophotography. The Vixen Extender PH works with the optical surface of a parabolic mirror to correct coma aberrations on Newtonian telescopes. It can transform the Vixen R200SS reflector into a research-grade f/5.6 astrograph with no false color. This extender provides a wide illuminated field of view with no dim images at the edges of the field of view, and the coma correction is perfect throughout the image circle.