The newly designed high definition ED lens on Vixen's ED115S Refractgor gives excellent optical performance with its Extra Low Dispersion (ED) glass. Chromatic aberration is virtually eliminated. The Sky at Night Magazine states: "Vixen's optics were excellent. The scope corrected false colours almost perfectly when in focus...Pointing the scope at the stars showed the optics to be pretty much perfectly corrected"*. The new ED lenses feature brighter images from the shorter f/7.7 focal ratio to capture crisp, pinpoint star images for your enjoyment. The ED115S Refractgor's lenses are made with environmently friendly technologies, free of hazardous lead that helps to support a cleaner global environment.