Telescope basics, reviews, accessories, and more!
Glass lenses were first created during the 10th century by the Greeks. As early as the 13th century eyeglasses were introduced to Europe, where the process of creation became more refined, as new methods for lens making and lens polishing were further developed.
Most people believe that the telescope was invented in 1609 by an Italian mathematician known as Galileo. However, in actuality it was invented in the Netherlands by Jacob Metius and Hans Lipperhey. There they applied for a patent of a tube which contained a convex and concave lens. This design is similar to the early nautical scopes used by sailors.
Galileo is credited with improvements to the original design, and for his usage in observing stars and planets. While the initial design was intended to be used for "seeing faraway things as though nearby," Galilei Galileo realized the advantage of studying the sky with the new object.
Galileo also quickly realized that if he created larger lenses he could see celestial objects even further away. And so the development of larger and larger telescopes began, a principle telescopes today are still based on.
Galileo's early advancement of the telescope is the reason why he is considered the "Father of Telescopes." This telescope developed by Galileo was an early version of the reflecting telescope as it used two lenses to capture and bend the light coming from different distant objects. The first telescope that Galileo created had the power to magnify an image up to three times. His last telescope was over four feet long and could magnify an image up to 30 times.
Galileo was not the only scientist creating telescopes at the time. In deed, many a telescope could be found in the finer eyeglass shops in Europe. But Galileo's telescopes were known for their quality and refinement.
There were several issues with the first telescopes:
In the 1611, Johannes Kepler introduced an idea of refracting telescopes in his book Dioptrice. The key to his change was to develop the telescope using two convex lenses... noting that the image would now be viewed upside down. He also changed the placement of the lenses. His telescope is known as the Keplerian telescope.
Kepler claimed that the advantages to his design would be a broader FOV (field of view) and ultimately that would improve the image quality. However, early scientists ignored his suggestion until Christoph Scheiner, a German mathemetician attempted to study sun spots with a version of the Keplerian telescope.
Scheiner found that using two telescope lenses, as described in Dioptrice by Kepler, increased the field of view and made an object in the sky much brighter. He also noted in his own manuscript, Rosa Ursina, published in 1630, that the image was in fact, upside down.
While an image being shown upside down was a difficulty for scientist observing objects here on earth, for scientists observing celestial objects, the upside down image posed no problem. It was at this time that the telescope began to take on the moniker "astronomical telescope," and those using them "astronomers."
While the Keplerian telescope resolved the issue with the FOV being so small, it created other issues.
The solution to this issue didn't come from scientists, it came from craftsmen. And it took decades to occur. Gradually, lens grinding and polishing techniques increased, until a specialized community of lens crafters, was able to output more spherical lenses, with a longer focal point, and decreased curvature.
These improvements had one problem, they required that the telescopes be even longer. Based on this fact, astronomers started thinking about making telescopes with bigger lenses. So in the late 1600s, telescopes were being manufactured that had bigger lenses and that were as long as 100 ft.
These long telescopes had many issues that scientists couldn't overcome. When the telescopes began to get over 50 ft in length, the slightest of wind would vibrate them. Adjustment of the long telescope was also quite difficult, and the astronomer searched for objects in the sky by trial and error.
As mentioned earlier, the problem of chromatic aberration was there in the refracting telescopes. This was resolved by Sir Isaac Newton when he proposed the idea of changing the lens of the telescope from a refracting lens to a reflecting lens.
He also introduced a way to improve the quality of the image without making the telescope much larger. The idea was to add some mirrors that could improve the quality of the image by collecting starlight. Telescopes that were made with reflecting lenses and mirrors were called Newton's Telescopes. Newton's Telescopes were relatively small telescopes but they almost had the same power as that of a larger telescope.
Reflector telescopes continued in use well into the 1700's. Even though Newton had designed a better telescope, other craftsmen and scientists were unable to grind mirrors of regular curvature. These mirrors at the time were made by adding arsenic to a copper-tin alloy. The arsenic made the mirror easier to polish, but the constant polishing affected the curvature of the mirrors further.
Two men would emerge in England that would improve upon Newton's telescope. The first was an inventor, John Hadley, who, after many trials, created a new style of mirror made from speculum, a compound of silver and bronze. His first telescope was a Newtonian telescope with a focal length of 62 inches and a diameter of 6 inches. It was said to "enlarge an object near two hundred times."
The success of Hadley's telescope was in his ability to polish the mirror in such a way as to create a refined parabolic shape creating little distortion. In telescopes, parabolic reflectors are used to collect starlight from a distant source and bring it to a common focal point, thus correcting spherical aberration found in simpler spherical reflectors.
The second prominent English man to dramatically improve upon the design of the Newtonian telescope was a musician, William Herschell. William eventually design a telescope of 20ft in length with a 19in diameter lens.
The use of metal mirrors caused severe issues with tarnishing, still requiring both men to polish frequently. Hadley had created multiple lenses for his telescope enabling him to use one while polishing the other. However, the amount of time spent polishing limited the popularity of this style of telescope.
Introduced by John William Draper, photographic telescopes gained enormous popularity amongst all astrologers.
John William Draper was successful in designing a telescope that would produce the Moon's image on a light-sensitive plate (photographic plate).
At that time, the exposure time was usually more than 10 minutes. Finally after an exposure time of 20 minutes, he was able to take what is regarded as the first photograph of moon ever taken. This was one of the greatest accomplishments in the telescope timeline.
There have been so many advancements in the timeline of telescopes. Most of the developments occurred before 1800 when technology was not at its peak as it is today. Today, with the advancements in telescopes, we can even see planets like Saturn and its beautiful ring.
Even we can see today the farthest planet in our solar system; Pluto. This timeline of telescopes will surely continue and will always continue with the ever increasing desire of human to see what has never been seen before.