The Galilean telescope is constructed around two lenses, a double-convex objective on the nose of the tube and a double-concave lens as the eyepiece. This arrangement produces an upright image. The telescope is limited, however, by a small field of view and relatively low magnification. Largely for this reason, the Galilean type configuration lasted to the twentieth century only as field binoculars and to the present day as theatre glasses. The Keplerian telescope of Johann Kepler is configured with two double-convex lenses. This results in an inverted image but the convex eyepiece provides a larger field of view and higher magnification, and an inverted image is not a distraction for astronomical or most maritime use . The Schyrle telescope, invented by Anton Schyrle around 1625, adds two additional double-convex lenses to the Keplerian style. This four-lens arrangement returns the image to an upright position. The telescope also had a reasonable field of view and higher magnification than other telescopes of its time and competed with the Keperian telescopes. In 1757 John Dolland, a prominent scientific instrument designer and manufacturer in London, combined a convex crown-glass lens with a concave flint (lead) glass lens to correct for chromatic aberration. From Dolland’s patent of the achromatic lens in 1758, telescopes began being manufactured with achromatic objectives and multiple plano-convex lenses in the eyepiece (typically 4 lenses). This new breed of instrument was called the achromatic telescope. By the early 1800s, Dolland was making 9.5-inch diameter refracting scopes, and by the late 1800s, large refracting telescopes with apertures of over 30 inches were being supplied to observatories around Europe and America. The Yerkes telescope on display at the Chicago Exhibition in 1893 was 40 inches in diameter, 50 feet long and mounted on a tower 30 feet high.

Hand held refracting telescopes are categorized by the number of retractable tubes they employ. Thus an instrument may be a single-draw, two-draw, three-draw and so forth. They are further categorized by the way lenses are arranged in the tubes as mentioned above. Very early telescopes were made of cardboard or wood covered with shagreen, vellum or leather. Bone, ivory or wood rings were used to hold lenses. From the 1750s to mid-1800s most telescopes were made of brass tubes with the front barrel encased in walnut, mahogany or fruitwood. Most telescopes made from the mid-1800s well into the 1900s were made entirely of brass with leather covers common on the front barrel. In the early to mid 1800s some naval telescopes, inscribed with ‘Day or Night’ on the drawtube, were designed for night and low light conditions. A three-draw telescope with red leather cover and gilt tooling, inscribed ‘1661’, is one of the oldest known surviving optical instruments and housed at the Maritime Museum in England.

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.