Celestron f/6.3 Reducer Corrector for C Series Telescopes This combination focal reducer and field corrector lens accessory works with all Celestron 5", 6", 8", 9 1/4", 11" and 14" Schmidt-Cassegrain telescopes This clever accessory makes it possible to have a dual focal ratio instrument, without sacrificing image quality The Reducer/Corrector is f/6.3 for C5, C6, C8, C9 and C11 telescopes and f/7 for the C14 telescope