Designed by British amateur telescope maker and astronomer George Carey, the Farpoint Carey Focus Mask can be used to quickly and easily focus your telescope for all types of astrophotography with DSLRs or imaging systems. Made of durable ABS plastic, the mask is designed to fit older 11" Classic Celestron Schmidt-Cassegrain telescopes (SCTs), and simply fits over the lens for use. It takes the guesswork out of focusing on astronomical objects and ensures tack-sharp stars, planets, and just about any other celestial subject you want to photograph or image.