The Sky-Watcher Pro SW 120ED APO 120mm ED Refractor Telescope is coveted for the superb contrast, high-definition and coal-black sky background that make stars appear like diamonds imbedded in black velvet. SW APO refractor utilizes the most modern optical glasses and fabricating techniques to deliver the ultimate in high-fidelity astronomical imaging. Subtle details pop as never seen before in telescopes of lesser optical capability.
The additional aperture compared to a 100mm diameter lens provides a dramatic increase in resolution and a heighten sense of seeing lunar and planetary surface phenomenon in seemingly 3D high-definition. In a given aperture size, refractors will always exhibit sharper images than other optical designs because the refractor concentrates more light into the central airy-disk and first diffraction rings. There is no diffraction pattern interference caused by a diagonal mirror, or secondary mirror being suspended in the optical path (central obstruction) as is the case with reflectors.
Sky-Watcher ED-APO refractor provides the finest images obtainable - bar none - in their design class. Sky-Watcher ED apochromatic refractor delivers dramatic coal-back skies and faithful, contrast-rich views of planetary and deep-space phenomenon that are second to none. Sky-Watcher ED-APO refractor is the logical choice as an investment in advanced instrumentation for exceptional viewing or photography. The Sky-Watcher ED-APO design assures virtual elimination of secondary, residual "false color" normally present in 2-element achromatic lens designs using Crown and Flint glass. Sky-Watcher APO refractor utilizes a second lens element made from the mineral fluorite instead of Flint glass. Fluorite, CaF2, is a halide with unique properties and a hardness of only four. It is an exotic and difficult material to fabricate into a lens.
Hence the cost of manufacturing a fluorite lens is quite high compared to a Flint lens element, for instance. Every lens element is individually inspected for purity and absence of striae and other image-degrading imperfections. Every lens is pitched polished to exacting standards of optical fabrication and performance by highly skilled opticians utilizing state-of-the-art methodology and rigidly controlled optical testing procedures.
The result is high-quality, diffraction-limited optics performing to the theoretical limits of their respective aperture sizes. All lenses are uniformly air-spaced in their cell housings. Using only the finest fabrication materials available, Sky-Watcher APO refractor is manufactured to painstakingly rigorous, exacting standards of optical and mechanical quality to insure the amateur astronomer peak performance and a great experience each and every time a Sky-Watcher ED-APO is taken into the field.