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The Sky-Watcher EQ5 102 AR Achromatic Refractor has unobstructed near textbook perfect diffraction pattern. This telescope delivers breathtakingly pristine celestial views with a dramatic coal-black sky background that makes stars glisten like diamonds. The SW 102mm refractor delivers performance second to none in its aperture size.
In fact, on lunar, planetary, double star and bright compact globular clusters this telescope will often perform on a par with a reflector up to perhaps 6.5". It will also resolve bright proto-stars and brilliant stars in prominent emission nebulae revealing nebulosity from surrounding gasses they illuminate. It is no wonder quality refractors are so coveted by serious amateur astronomers. Sky-Watcher's Crown (BK7) and Flint (F2) achromatic lenses are fabricated to the highest optical standards from Grade-A glass free of striae and other image-degrading imperfections.
Each lens set is individually pitch-polished and hand figured by a master optician ensuring diffraction-limited premium optical performance that is second to none worldwide. All lenses are uniformly air-spaced. Each optical lens surface is coated with exotic anti-reflection metallic coatings (fully coated) to ensure the optimum light through-put. Four layers are applied to each surface (Magnesium Fluorite, MgF2 and Hafnium Dioxide, HfO2). The proprietary Sky-Watcher "Metallic High-Transmission Coatings" (MHC) are the finest photon anti-rejection coatings in their class.
The objective lens cell is light-baffled to reject stray, unfocused light. The draw tube is likewise baffled to insure optimum contrast. The tube's interior is flat blackened to help prevent unfocused internal light reflections from reaching the focal plane. The optical tube is aluminum, powder coated reflective gloss black with gold fleck accent. The front and back cells are cast aluminum painted black. Optical focus is achieved by means of a mechanically ultra-smooth, backlash-free, precision 2" Crayford-style rack & pinion focuser assembly.