Evolution of the Telescope
By Rachel Alexander
Galileo - The First Refracting Telescope
However, they did have a few flaws, such as a narrow field of view, blurry and distorted images due to the spherical shape of the lens, called spherical aberration, and rings of color surrounding objects, caused by the way light travels through glass, called chromatic aberration.
Spherical Aberration - Distorted Image
Photo taken by the Hubble Space Telescope.
Spherical Aberration - Corrected Image
Photo taken by the Hubble Space Telescope.
The use of two convex lenses had some problems though. It didn't fix the chromatic aberration, and it made the resulting image appear upside down.
*Fun fact: Kepler never actually built his telescope. It was first built a few years later by Christoph Scheiner.
- Later designed the compound eyepiece. An eyepiece that uses two lenses instead of one. After it was built in 1703, several years after his death, it became standard equipment for large telescopes for some time.
-Designed and built several massive refracting telescopes: a 125 ft, a 180 ft, and a 210 ft telescope. These were more powerful, but were also too large to put in a metal tube, they were unwieldy, and would lose the image in even the slightest breeze.
Isaac Newton - First Reflecting Telescope
Later, he added a flat, diagonal secondary mirror that would bounce the light out to the side of the telescope into an eyepiece. Is made it so that his head wouldn't get in the way of the reflected light.
Laurent Cassegrain - Cassegrain Reflector
- Chester Moore Hall
In 1733, Hall combined two different types of glass in a lens that reduced the optical distortions it created.
- John Dollond
In 1758, Dollond patents the Achromatic lens, although, there is some controversy as to if he developed it independently or borrowed the design from Hall.
Eponymous Eyepiece - Ramsden Eyepiece
- A plano convex singlet eye lens
- A cemented convex-convex triplet lens (3 pieces put together)
This eyepiece gave near perfect image quality, but had a narrow field of view.
Ritchey-Chretien Reflector Telescope
The telescope introduced the Coude System, which allowed scientists to deflect the light from the telescope to many other instruments that were too heavy to attach to the telescope itself and analyze it.
Hooker 100 inch Reflector Telescope
The delay was partially due to the fact that the 100 inch glass disk made to become the mirror had hundreds of tiny air bubbles inside it, and some of the glass crystallized, this meant that the disk would not be able to stand up well to the grinding it would need to become a mirror. After several other failed attempts at making a new disk and being delayed further by World War One, they finally decided to use the original mirror and begin the five year processes of grinding it and coating it in silver to turn it into a mirror.
The finished mirror had a diameter of 100 inches, and the entire telescope weighed 100 tons. The motions of the dome, shutters, and telescope were controlled by a system of 30 motors.
Hale 200 Inch Reflector
COBE - Cosmic Background Explorer
- one to observe infrared radiation
- one to map microwave radiation
- one to measure the cosmic background radiation's spectrum
The COBE orbited at 547 miles above earth, but was not very sensitive, and was eventually decommissioned in 1993.
HST - Hubble Space Telescope
A series of coin sized mirrors were placed in front of the original instruments and corrected the image.
Has been upgraded several more times since then to gives us even better images.
CGRO - Compton Gamma Ray Observatory
Unfortunately, it had to be brought back to Earth in 2000 because one of it's gyroscopes failed.
Spitzer Space Telescope
Kepler Telescope Diagram. Digital image. Amazing Space. Web. 09 May 2016. <http://amazingspace.org/resources/explorations/groundup/lesson/basics/g9a/graphics/g9a_kepler.gif>.
Plano Convex. Digital image. Molecular Expressions. Web. 9 May 2016. <https://micro.magnet.fsu.edu/optics/lightandcolor/lenses.html>.
Plano Concave. Digital image. Molecular Expressions. Web. 9 May 2016. <https://micro.magnet.fsu.edu/optics/lightandcolor/lenses.html>.
Hubble Spherical Aberration. Digital image. Hubble Space Telescope. Web. 9 May 2016. <http://www.spacetelescope.org/about/history/aberration_problem/>.
Chromatic Aberration. Digital image. Nikon. Web. 9 May 2016. <http://www.nikon.com/products/sportoptics/how_to/guide/binoculars/technologies/img/technologies_08/pic_011.jpg>.
COBE Telescope. Digital image. NASA. Web. 10 May 2016. <http://science.nasa.gov/missions/cobe/>.
Hubble Restored. Digital image. Hubble Space Telescope. Web. 10 May 2016. <http://hubblesite.org/gallery/spacecraft/04/>.
Compton Gamma Ray Observatory. Digital image. NASA. Web. 10 May 2016. <http://nssdc.gsfc.nasa.gov/nmc/spacecraftDisplay.do?id=1991-027B>.
Chandra X-ray Observatory. Digital image. Chandra X-ray Observatory. Web. 10 May 2016. <http://chandra.si.edu/about/spacecraft.html>.
Assembly of Telescope. Digital image. NASA. Web. 10 May 2016. <http://www.nasa.gov/centers/jpl/missions/spitzer.html>.
Gregorian Design. Digital image. Wordpress. Web. 10 May 2016. <https://thonyc.wordpress.com/2012/06/21/reflecting-the-heavens/>.
200 Inch Telescope, East. Digital image. Palomar Observatory. Web. 10 May 2016. <http://www.astro.caltech.edu/palomar/media/halemedia.html>.
Hooker 100 Inch. Digital image. Joe's Big Idea. Web. 10 May 2016. <http://www.npr.org/2015/04/25/401843663/hubbles-other-telescope-and-the-day-it-rocked-our-world>.
RCT. Digital image. Wikiwand. Web. 10 May 2016. <http://www.wikiwand.com/en/Ritchey–Chrétien_telescope>.