The Celestron Dew Heater Ring is the ideal dew prevention solution for your Celestron telescope. This must-have accessory will improve your observing or imaging nights year-round. The Dew Heater Ring permanently mounts to your 11" Celestron Schmidt-Cassegrain, EdgeHD, and RASA optical tube, replacing your retaining ring, so you'll never be caught without it. The installation process is quick and easy.