Designed for both astronomical and terrestrial use, Pentax's 8x40 /10x50 /12x50 /20x60 SP S-Series WP Binocular can be used with confidence in all weather and conditions. The large oversized 40mm (8X40) /50mm (10X50, 12X50) /60MM (20X60) objectives are fully multicoated to reduce reflection and maximize light transmission through the entire optical path. Utilizing the traditional porro prism configuration gives scenes a rich depth of view for an immersive observation experience and provides a comfortable feel in the hand with a lot of surface area to maintain a sure grip. The large objectives and coatings maximize the amount of light getting to the user's eyes for exceptional low-light capabilities, and its high 10x magnification provides an immersive observation experience. Complementing the optical performance are construction details made for the trail. The optical tubes are nitrogen-filled and O-ring sealed for fogproof performance and to make them submersible to as much as 3.3'. The binocular sports a generous 20mm eye relief and the fold-down eyecups seal against the ocular cavity to block stray peripheral light which can dim images and effect night adjusted vision for 10x50, 12x50 & 20x60.