Celestron's Sky Master series of large aperture binoculars are phenomenal value for high performance binoculars, & ideal for astronomical or terrestrial use, especially over long distances. Each Sky Master model features high quality BAK-4 prisms & multi-coated optics for enhanced contrast. Celestron has designed & engineered the larger Sky Master models to meet the special demands of extended astronomical viewing sessions, large objective lenses, high magnification, in a reasonably lightweight configuration.