Pennsylvania Game News - August 2010 - 35

set side by side in a single tube or box about two feet long and mounted on a stand. One was highly decorated and presented to a grand duke. The next news of the binocular was in the 1750s, when an optician joined two small telescopes with a rudimentary hinge. Although adjustable for the user’s eyes, it probably was easily knocked out of alignment. Interest in making a binocular was renewed in the early 1800s. At the time, the small telescope called the opera glass, or spyglass, was popular with theatre goers. The first opera glass was a single-barreled telescope a few inches long that magnified about three times. It had an achromatic lens, invented in the mid-1700s, which removed the color fringe that old lenses created around a bright object. In 1823, two opera glasses were successfully joined by metal bridges. With this new opera glass, or “pair of opera glasses,” theatre goers could use both eyes to get a closer look at the performers. Within a few years opera glasses had a center wheel for focusing. A few were hinged to adjust to the user’s eyes, but the nonadjustable opera glass was usually suitable because the space between the eyepieces fit most persons. Still, shoppers often tried various models “for size.” Most opera glasses were painted black or covered with colored leather. It was the fashionable lady who was seen holding an opera glass encased in motherof-pearl and fitted with a folding handle. The opera glass had a sporting cousin called the “field glass.” Built somewhat sturdier and magnifying up to about five times, a field glass was meant for outdoor use. Outdoor magazines of the time told their readers that a field glass would give them a better look at wildlife, nature and scenery. Ads in the magazines showed the wide selection available. Field glasses often had names, such as “marine glass,” “hunter’s glass,” or “bird glass.” The “Long John” and “Deer Stalker” of the late 1800s were about a foot long, with long eye-tubes, and magnified as much as
AUGUST 2010

16 times. They were said to be awkward to use and easily knocked out of alignment. Amateur astronomers were reminded that an opera glass or field glass could also be used for stargazing. The dawn of using prisms along with lenses began in the 1850s, when the Italian artillery officer Ignazio Porro wanted to shorten the length of long draw-tube telescopes. He developed prisms that folded the light path so that a telescope could be compact and easier to hold. Porro wasn’t interested in making a binocular, but others tried using his prisms. They weren’t successful, though, because making high quality matching prisms was too difficult at the time. But Porro’s prisms stirred German interest in making a prismatic binocular. Ernst Abbe provided the idea. Otto Schott produced the high quality glass, and Carl Zeiss had the manufacturing skills needed to bring everything together to make the revolutionary binocular that made its debut in 1894. Their prismatic binocular had the classic design that persists today: two objective lenses set apart farther than the eyepieces and a hinged body to adjust for eye spacing. Separating the objective lenses by using prisms not only made a compact instrument but also enhanced the stereo effect. Early names for the Zeiss binocular were cumbersome, such as “stereoscopic binocular field glass” and “stereo prism binocular.” But a simpler name was found: “Feldstecher,” which means “field glass.” Zeiss binoculars, finely made and easy to use, were an immediate success. The early models had objective lenses ranging from 11 to 20 millimeters in diameter, and magnifications from four to eight power. They also had a wide field of view. Other models followed, some with rotary eyepiece selectors for changing the magnifica35

Pennsylvania Game News - August 2010

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