The History of Telescopes

| May 19, 2015

Since their conception in the seventeenth century, telescopes have come a long way. In fact, the properties of light, such as color, reflection, and refraction, have been known since Ptolemy wrote about them in the second century. These principles serve as the foundation of modern telescopes, but it has only been since the early 1600s that the first practical telescopes have come into being. Then, in 1990, one of the best known telescopes was launched into space to orbit around the earth, the Hubble Space Telescope. Many famous scientists over the years have given their unique contributions to the development of the telescope including Galileo and Isaac Newton. Telescopes have a fascinating and varied history.

Galileo And His Telescope

Galileo And His Telescope

When was a telescope first used

It is difficult to trace the beginnings of the telescope to one specific event. Humans have been toying with glass and its effects on light for many centuries. However, it was not until the fourteenth and fifteenth centuries that glass began to be used for practical purposes when convex lenses were developed to fix farsightedness and concave lenses were used to fix nearsightedness. The beginning of the modern telescope as we know it is accredited to the Netherlands in 1608. That was when Hans Libbershey, an optician, discovered that holding up two lenses some distance away from each other makes distant objects appear closer. This is the first documented invention of a telescope, but Libbershey’s application for a patent was denied. Other men who are credited with the first telescopes include Jacob Metius and Zacharias Janssen.

Galileo and telescopes

These early telescopes were refracting ones that were made of a convex objective lens and a concave eyepiece. To focus, the telescopes slid inside themselves. Libbershey’s design only had a magnification of 3x, and those original telescopes from the Dutch did not invert the image. They eventually found their way all over Europe. Then in 1609, Galileo improved these designs and used them to observe the stars. Consequently, Galileo is credited with inventing the first astronomical telescopes. Galileo’s first telescope design included a convex lens in one end of a heavy tube and a concave lens in the other. Galileo continued to improve on his designs until he had one with a magnification of thirty-three diameters. Galileo made many important astronomical discoveries with his telescopes including the phases of Venus and the moons of Jupiter. Galileo also become a proponent of the heliocentric model of the solar system in which the sun is at the center.

Improvements to Galileo’s telescope

Galileo’s instruments were the first to be called telescopes by Prince Frederick Sesi, and the term means far seeing. In 1611, Johannes Kepler made his contribution by introducing some practical advantages of telescopes and building them with concave eyepieces instead of convex. This allowed for larger images but inverted the image so another lens had to be added. Throughout the rest of the 1600s, more designs of the telescope came into being, mostly notably from Rene Descartes, Christiaan Huygens, and Robert Hooke. These men experimented with different models of telescopes, although most of them followed Kepler’s design with compound eyepieces.

Isaac Newton’s new telescope design

In 1668, Isaac Newton became the first person to successfully develop a reflecting telescope. He used a concave spherical mirror about two inches in diameter, a flat secondary mirror set at an angle, and a convex eyepiece lens. These telescopes proved to be superior to refracting lenses in that they magnified objects in greater amounts than could ever be done by a lens. Even though mirror telescopes produced poor qualities of images, they fixed many problems encountered by telescopes with lenses. The mirrors also had to be polished fairly often. James Short improved upon Newton’s reflecting telescope in 1730 by inventing a parabolic and elliptical mirror with no distortions. These were ideal for reflecting telescopes.

Refracting telescopes

Refracting telescopes became popular again in 1729 when Chester Moor Hall developed an achromatic lens. Hall combined two pieces of glass with two different indices of refraction in order to produce a lens that focused most color at an almost precise point. The image still was not perfect, however. In the nineteenth century, various individuals worked on improving the designs of telescopes, improving both lenses and mirrors and how much telescopes could magnify objects.

New styles of telescopes

The twentieth saw the development of a whole new kind of telescopes, ones for a wide range of wavelengths from radio waves to gamma rays. Grote Reber invented the first radio telescope in 1937, and fascination with radio astronomy exploded after World War II with the develop of large dishes. One of the biggest includes the 1000-foot Arecibo telescope in 1963. 1991 saw the first Gamma Ray telescope at the Compton Gamma Ray Observatory. X-ray telescopes have been around since the 1940s, and ultra-violet telescopes were developed in the 1960s and 1970s. The first infrared telescope to be launched into space was the IRAS satellite in 1983.

Science and the future of telescopes

The National Academy of Science in the U.S. in 1962 recommended the development of a large telescope that could operate from space. It took a few years until 1977, for Congress to approve the funding. Almost thirty years later, in 1990, the Hubble Space Telescope was deployed by astronauts in the space shuttle Discovery and put into orbit 380 miles above the earth. Telescope designs are constantly improved on even day. In 2008, Max Tegmark and Matias Zaldarriaga proposed a telescope in which mirrors and lenses are replaced completely by computers. No matter what form they take in the future, telescopes will continue to let us explore our universe.



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