Check the Field of View (FOV).When you look through a pair of binoculars, a circle surrounds the object being viewed. The diameter of that circle at a distance of 1,000 yards is called the field of view, or FOV. A larger FOV helps keep objects inside the circle, even when your boat rolls or pitches in waves and swells. Purchase binoculars with a specified FOV between 350 and 450 feet at 1,000 yards.The most common marine binocular powers are 7 × 50 and 7 × 35. The first number shows the amount of magnification of a viewed object. You'll need magnification of 6 or 7; anything higher causes objects to jump out of the FOV.The second number is the diameter of the larger lens, or objective lens. This indicates the instruments ability to gather light at twilight or nighttime and in haze or fog. Larger is better. Look for an objective lens diameter of 35 to 50 millimeters.

Are All Rubber Coated Binoculars Waterproof? Rubber coating provides the user with a better grip and protects against damage. Waterproof binoculars come charged with nitrogen to prevent intrusion into the prism or lens housing. Read the specifications and avoid binoculars bearing the much less protective "water-resistant" claim. You want waterproof, not just water-resistant, binoculars, and you'll be glad you spent a few dollars more after spray or a squall douses them.Eyeglass wearers should choose rubber-coated binoculars with the fold-down eye-cups. These help improve focus and provide comfort when bracing the binoculars against glasses.

How to Focus Binoculars to Perfection.Binoculars come with center focus or individual focus eyepieces. Center focus makes adjustment easier and readjusting unnecessary as your viewing range changes. Many fine professional marine binoculars, however, come with individual focus lenses. They just take a bit longer to adjust and need readjustment at different ranges.Take the time to learn the adjustment process for both types of instruments. Now you can select the perfect pair that will give you satisfaction for years to come.
 

Source: Waterproof Binoculars,   Monocular Telescope