Pentax 8.5 x 21 Papilio Butterfly Series Binocular

Pentax Papilio binoculars are the perfect choice for insect observation in the field and in museum and galleries. The enhanced observation capability of the Papilio binoculars is made possible by a Pentax Convergent Lens Optical System Engineering CLOSE mechanism. CLOSE automatically slides the left and right objective lenses toward the center when the focus is fixed at a short distance. Revolutionary, dual axis, single body housing with synchronized eye piece adjustment to assure correct optical alignment for comfortable viewing. Fast and easy center focusing for handling ease. Helicoid eyepiece rings for extra viewing comfort. Fully multi coated optics to eliminate harmful ultraviolet rays while improving light transmission for high contrast images with no glare. High quality BaK 4 prisms transmit more light at the edges to enhance illumination. Tough rubber coated exterior provides a sure grip and protects the internal mechanisms. Includes neck strap, carry case, and eyepiece lens caps.Specifications: Type: porro prism center focusing Objective lens: 2 elements in one group Eyepiece lens: 5 elements in 5 groups Magnification: 8.5X Objective lens diameter: 21 mm Angle of view: 6.0 degrees Apparent field of view: 51 degrees Field of view 1000 m: 105 m Field of view 1000 yd: 315 ft Exit pupil: 2.5 mm Eye relief: 15 mm Prism: BaK 4 Multi layer coating: yes Relative brightness: 6.3 Diopter adjustment range: click stop adjuster in eyepiece Eye distance adjustment range: 2.2 2.9 Focusing range: approx. 0.5 m to infinity Eyepiece ring: helicoid type Vergence correction: focus coupled correction mechanism Water resistant: yes Weight: 10.2 oz.