Binoculars used for astronomy rate as high as 30 x 100, or 30 times magnification with a 100 millimeter diameter lens. While many stargazers prefer the stability and potentially greater magnification of a telescope, a powerful pair of astronomical binoculars allows a user to take quick glances at celestial objects without the need to extend tripod legs. The necessary size, though, of astronomical binoculars limits their portability and increases the need for tripods of their own for long viewing sessions. For this reason, most astronomical binoculars are designed for use with tripods.
Marine and Military
Military binoculars run a wide range of sizes and power, as variable as the missions of the military services themselves. Because they are designed for optimum performance mostly regardless of cost, military binoculars feature easy handling, watertight sealing, ruggedness, durability and glare reduction, among many other factors. Giant binoculars of 18 or 20 power or more might be used for such missions as border patrols or distant targeting as much as a mile away. Marine binoculars rate consistently around 7 x 50, offering plenty of light introduction.
Hunters using binoculars need them to be lightweight, waterproof and durable, and as such the optics they choose often mimic military or marine designs. Hunters tend to select binoculars in the middle ranges of magnification and diameter, typically 8 x 42 or 10 x 42. Hunting binoculars also feature camouflage exterior designs and hunting specific tools such as laser rangefinders.
While not as varied in their pursuits as military personnel, birders, depending on their areas of interest, use binoculars of different powers and diameters. A birder who generally focuses on backyard feeders, birdbaths, shrubs and trees should consider binoculars with 7 times magnification, as anything greater than that power might make focusing and location of a bird in such close quarters difficult. Birders who venture beyond the yard to open spaces like fields, meadows, beaches and even offshore on pelagic birding excursions might consider slightly more powerful optics. Mountaintop hawk migration watchers easily rate the need for even higher magnification and diameter, as their target sights tend to be more distant than those of the average birder.