The Renaissance The telescope is an optical instrument used to make distant objects appear closer made of lenses and curved mirrors. The first telescope was created in 1609 by Galileo and used it look into the night sky. He based his design on the recently invented spyglass and made his telescope stronger than it so that he could use it to look up at space. He used the telescope to make many significant discoveries, like the rings of Saturn and sunspots.
While the telescope was a major instrument for astronomy, there was a problem with it, the problem of chromatic aberration, the fringes of color that surrounded bright objects seen through a glass lens. As light passes through a lens, it breaks up into various colors because the glass bends the colors by different amounts, and this caused problems with the telescope. To fix this problem, Isaac Newton created a new telescope with the primary lens replaced with a polished, round metal mirror. He experimented with different mixtures of metals and decided on the combination that was six part copper and two parts tin. It was almost as bright as expensive, quick-to-corrode silver and would reflect a lot of light. The more light reflected by the mirror, the better the would be.
While the problem with chromatic aberration was fixed, there was another problem that Newton couldn't fix, spherical aberration, the blurry view caused by the spherical shape of his primary mirror. It took John Handley in to fix the problem, years after Newton made his telescope. To keep his head from getting in the way of the reflected light, Newton added an extra mirror, the secondary mirror, that bounced the light out the side of the telescope, into the eyepiece. Newton's telescopes wasn't used by many in his time, and their purpose was more to prove Newton’s ideas about telescopes than to view the sky. Other scientists would improve Newton's design before these types of telescopes became popular, we still call them Newtonian reflectors, after their creator. |
Galileo's Telescope
Newton's Telescope
|
The Leviathan of Parsontown
The Melbourne Reflector
|
During the Industrial Age, the use of metal mirrors in telescopes allowed them to become more powerful and better. But during this time was also the Industrial Revolution where manufacturing and industry was spreading across Europe and people started to use machines to complete tasks, and this didn't exclude making advancements with the telescope.
The biggest development with the telescope during this time was the creation of the parabolic mirror. The Parabolic mirror fixed the problem with spherical aberration, something that Newton and Galileo couldn't fix in their time. The parabolic mirror curves differently than a spherical mirror. Light rays that bounce off the edges and center all meet at the same point, making the image clearer. When astronomers learned how to make these mirrors ,they could create telescopes without chromatic aberration and spherical aberration. These telescopes also had smaller focal lengths, making it easier to use and compact. Astronomers began to also make bigger telescopes because they were making bigger primary mirrors. With bigger mirrors, more light could be collected. With bigger mirrors, the telescope could see objects from even further away, making bigger telescopes stronger than smaller ones. The problem with bigger telescopes was that the astronomers weren't able to maneuver them easily to look around the sky. Another problem with the big telescopes was that they've become powerful enough that the atmospheric distortion became a problem. Atmospheric distortion happens because of moving pockets of air in the atmosphere. As light passes through those shifting pockets, it bends in unpredictable ways. While using the telescope with the problem of atmospheric distortion, the images appear blurry. One discovery in the 1900's was that the stars in space gave off static as they moved and that they could use the radio waves to see the stars and celestial bodies. Telescopes then had a parabolic reflector to catch the radio waves, then they would bounce off the dish and meet at a single point, the focal point, where a receiver has been carefully positioned to capture them. The receivers record information, just as a camera or a charge-coupled device (CCD) would in other types of telescopes. Since the incoming waves are faint, the receiver amplifies them before sending the signal to a computer that stores the data. There were some advantages in having a radio telescope, like the fact that you could use them during the day and that they brought out clearer images.
|
Hubble Space Telescope
Large Binocular Telescope
|
Eventually, enlarging telescopes no longer improved our view… all because of the Earth's atmosphere. Telescopes here on the ground are affected by the atmosphere distorting the light rays when they pass through the atmosphere. There is only one solution to this problem, putting a telescope in space.
In the 1970s the European Space Agency and the National Aeronautics and Space Administration started to work on the Hubble Space Telescope. Twenty years later, in the 1990's, five astronauts boarded the space named Discovery and put the Hubble Space Telescope into orbit roughly 380 miles (600 km) above the Earth's surface. With this telescope in space, there is nothing that can distort images seen by the telescope and it has produced images that are unmatched by other telescopes. This great accomplishment was only possible because of the scientists, engineers, contractors, and institutions from all over the world who worked on this project for two decades. While the Hubble Space Telescope is able to produce amazing images because it is in space, there is a telescope on the ground that is stronger than the space telescope, the Large Binocular Telescope. The LBT is located in Arizona and is able to produce images that are 3 times sharper than the ones produced by Hubble while only using one of it's two lenses. Using both of its lenses, it is able to produce images that are 10 times as sharp as the ones produced by Hubble. While it is on the ground, the technology used in the LBT allows it to go through the problems of the atmosphere and take pictures that are much better than the ones Hubble can produce. |