The original opera glass was designed in the early 1700s as a simple small monocular telescope based on the Galilean two-lens system. Typically opera glasses only focus 2 to 3x. They were intended from the start to be elegant and many are ornately decorated with enamel scenes or gilded with gold. Some are clad in silver, pewter, ivory, tortoise shell or mother-of-pearl. The first reflecting telescope, which began to compete with the refracting type, was invented in 1663. It used mirrors to collect light instead of a lens. A few years later in 1669, Issac Newton advanced the concept with a different mirror configuration, producing the first truly practical reflecting scope, the Newtonian telescope. One of Newton’s designs was only 6 inches long but could magnify 40x which was comparable to the magnification of 6-foot long refractory scopes at the time but without the distracting aberrations inherent to glass lenses. Large reflecting astronomical telescopes took on various mirror configuration and were in use by the mid-1700s. William Herschel was using Newtonian telescopes to penetrate space at the end of the eighteenth century, and large diameter reflecting telescope mirrors were widely applied to astronomy throughout the nineteenth and twentieth Centuries. The largest single mirror in a reflecting scope is the 6-meter diameter Russian reflector in the Caucasus Mountains, constructed in 1976.