The ED "S" apochromatic refractor features Extra-Low Dispersion (ED) glass in its objective lens to suppress chromatic aberration...
The ED S apochromatic refractor features Extra-Low Dispersion (ED) glass in its objective lens to suppress chromatic aberration to...
The Vixen ED103S is an apochromatic refractor, with fantastic contrast and 4" aperture, sufficient for viewing most of the planets...