Development History of the Telescopes and Its Functions

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  • Topic: Reflecting telescope, Refracting telescope, Telescope
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  • Published : April 9, 2012
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A ground breaking new tool used to study the heavens was introduced in the 17th century. This tool was known as the telescope. It revealed the cosmos in a different way than our naked eye could ever perceive. The telescope opened doors to countless stars, nebulae, galaxies, and a slew of never before seen wonders. With its creation came limitations and caused the need to improve and upgrade the methods in which the telescope functioned and find new ways of viewing the heavens.There are three main types of telescopes; refractor telescope, reflector telescope and compound telescope, also known as catadioptric telescopes. Each of these telescopes has a main function which is its ability to gather light. The telescope also has resolving power, which allows the telescope to reveal details in objects and a magnifying power, which scales the object in size through the telescope. Every telescope has these functions, but over time humans advanced their technology over time and learned to produce larger telescopes to enhance the functions and develop new ways to construct telescopes to see even the faintest objects in the heavens.

In the thirteenth century the lens was called “lentils of glass” which translated in Latin to “lenses.” The spyglass utilized a convex lens and was primarily used among the elderly who had succumbed to eyesight problems. The lens was small and had a noticeable green tint caused by the iron in the glass; the lens was also daunted with air bubbles. By the fourteenth century, magnifying glasses were seen as a “symbol of wisdom and respect.” In the mid-fourteenth century the two-lensed spectacle had appeared out of Venice, where scholars and noblemen were seenas educated if seen wearing them. At the turn of the fifteenth century the concave lens appeared and the study of optics halted (Hardman, 1).

The first telescope emerged with a patent application by Hans Lipperhey who in 1608 was credited with the invention of what he called the “spyglass.” Lipperhey’s device featured two concave mirrors arranged as to amplify the light it gathered by compressing it in a small area. Spyglasses after Lipperhey could magnify light up to two and three powers, which was not powerful enough to see the craters on the moon. The first telescope emerged with a controversy between Hans Lipperhey and Jacob Metius. It can be argued that Hans Lipperhey was not the inventor of the first telescope because there was no documentation of when he invented it. However, because there is no documentation of Metius’ inventing of the telescope, Lipperhey receives the credit for being the first to submit a patent application. (“Galilean Telescope”)

Fig. 1. Galileo’s Telescope and its Functions
The spread of news about Lipperhey’s telescope finally reached an Italian professor and experimenter Galileo Galilei who saw a way to improve on Lipperhey’s design. In April 1609, Galileo constructed a small tube that contained a convex objective lens and a concave eyepiece (Fig. 1.).His telescope used refraction to bend the incoming light as it traveled through the lens. Galileo’s latter telescope could magnify light up nine times. With his telescope Galileo was able to see the craters on the moon. With his telescope came some setbacks. His refractor had a small field of view (could only see part of a full moon at a time). Images of stars appeared blurry and were surrounded by “color haloes.” The color haloes is known as chromatic aberration, it occurs when light is bent from the primary lens and not all the light is bent back to the same point when bending through the eyepiece. Even so, Galileo continued to improve on his telescope and created one that could magnify up to thirty times (“The First Telescope”). (“Field Lens Telescope”)

Fig. 2. Telescope design using a field lens
In 1611 Johannes Kepler published a book title “Dioptrice” where he suggested an alternative to the Galilean telescope. Kepler’s telescope design used two convex lenses...
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