A larger objective lens means more light-gathering power, and you can see sharper and brighter images. Extra-Low dispersion can effectively prevent images from producing chromatic dispersion and restore the most realistic and brightest image colors. The BAK4 prism removes glass effctively internal lighting reduces light losses.Its refractive index can reach 99.6% Super-Multi Coated Glass means multiple coatings on all lens surfaces. And all air-to-glass surfaces are anti-reflective multi-layer coated. Super multi-coated lenses are typical of high-end optics. The interior of this is filled with nitrogen and sealed The laboratory is waterproof for 30 minutes at a depth of 1 meter It is not afraid of wet and rainy environments effectively extending the service life of the telescope.