Meade 152ED (600 x 152mm) Telescope

It has long been known that the refracting telescope is capable of yielding perhaps the finest optical imaging performance of any telescope design. Because, however, light passes through the lens elements of a refractor (as opposed, for example, to the design of the Newtonian reflecting telescope, where light is reflected by two mirrors), chromatic aberration has traditionally had a significant, negative effect on optical performance. It was not until the early-1980s, however, with the advent of ED (Extra-low Dispersion) glass, that truly first-rate apochromatic (color free) objective lens designs became physically realizable in moderate apertures and at reasonable pricing levels. More than three hundred years after the invention of the refracting telescope, it was the development of ED glass, more than any other advance, that finally allowed the basic refracting telescope design to reach fruition.