Celestron skymaster binocular 15x70 features high quality bak 4 prisms and multi coated optics for enhanced contrast the celestron skymaster model has been designed and engineered to meet the special demands of extended astronomical or terrestrial viewing sessions carrying case included each pair of celestron skymaster binoculars feature high quality bak 4 prisms and multi coated optics for enhanced contrast clear sharp views and ultra sharp focus across the field of view specificatio