With a 5-element optical layout designed specifically for the EdgeHD 11", this 0.7x Edge HD Reducer Lens from Celestron maintains flat-field performance and helps reduce exposure time by half. This accessory telescope eyepiece threads directly to 3.25" threads of EdgeHD, reducing mechanical vignetting and allowing for use with full-frame sensor cameras and off-axis guiders, as well as your existing Edge HD T-adapters .