Refracting Telescope Is A Favorite

Refracting Telescope
Refracting Telescope

Celestron PowerSeeker 70EQ Refracting Telescope

The refracting telescope (also called a refractor) is a special type of telescope that is characterized by it'a long, straight tubular body.  It is uses a large lens at one end of the tube to capture light from the image being viewed, while the viewer is positioned at the opposite end with an smaller lens (eyepiece).

History

Although the exact inventor of the refracting telescope is not known, Hans Lippershey is generally credited with the creation of the telescope due to the fact that he was the first person known to have documented a written record of the device as part of a patent that he filed in the year 1608.

Throughout history there have been many famous astronomers and scientists that have made significant contributions to astronomy thanks in part to the functionality of the refracting telescope.

Design And How Does It Work

The design of a refracting telescope is constructed from a tubular body, placement of a main objective lens at one end tube and a small eyepiece lens at the opposite end. The viewer uses the telescope by aiming it with the objective lens closest to the object. The viewer then peers through the eyepiece lens as the captured images directly through the tubular body.

refracting telescope

The refracting telescope does not contain any mirrors, but instead bends the light rays from the image along the length of the tubular body such that the focal points of the lenses coordinate to produce a magnified image.

The magnification of the object being viewed is accomplished via a relationship between the objective and eyepiece lenses. A refractor's magnification may be calculated by dividing the focal length of the objective lens by that of the eyepiece. For a more detailed explanation and examples of magnification calculations, be sure to read our other article on calculating the maximum useable magnification of a telescope.

Advantages

  • Refractor telescopes are very stable. After their initial alignment, the optical system is more resistant to misalignment than the reflector telescopes.
  • The tube has an airtight seal to protect the inside from any dirt or moisture. This results in the glass surface of the lens inside the tube very rarely, if ever, requires any cleaning. 
  • Additionally, because tube is closed off from the outside environment, air currents and effects due to changing temperatures are removed and no longer an issue. The results is that images are clearer, steadier and sharper than those from a reflector telescope of the same size.

Disadvantages

  1. All refractors suffer from an effect called chromatic aberration (``color deviation or distortion'') that produces a rainbow of colors around the image. Because of the wave nature of light, the longer wavelength light (redder colors) is bent less than the shorter wavelength light (bluer colors) as it passes through the lens. This is used in prisms to produce pretty rainbows, but can it ruin an image! There a couple of ways to reduce chromatic aberration. One way uses multiple compensating lenses to counteract chromatic aberration. The other way uses a very long objective focal length (distance between the focus and the objective) to minimize the effect. This is why the early refracting telescopes were made very long.
  2. How well the light passes through the lens varies with the wavelength of the light. Ultraviolet light does not pass through the lens at all.
  3. The thickness of the objective lens has a direct effect on how well light passes through it.  The amount of light decreases as the thickness of the lens increases.
  4. It is extremely difficult and expensive to manufacture a glass lens with no imperfections inside the lens, that also has a perfect curvature on both sides of the lens. As a result, less expensive refracting telescope often contain an inferior objective lens which results in distorted images.
  5. By design, an objective lens is only supported only at the edges. Unfortunately overtime, the glass of the lens will sag under its own weight resulting in image distortion.

A refracting telescope is a great tool for anyone wishing to view the sky, planets, and stars above. Many people enjoying owning and using a refracting telescope because it's sturdy construction is resistant to misalignment, and they generally require relatively simple maintenance. 

Be sure to check out our comprehensive Telescope 101 Guide for more information about all aspects of telescopes, including history, construction, components, plus care and maintenance tips.

Advantages

  • Refractor telescopes are very stable. After their initial alignment, the optical system is more resistant to misalignment than the reflector telescopes.
  • The tube has an airtight seal to protect the inside from any dirt or moisture. This results in the glass surface of the lens inside the tube very rarely, if ever, requires any cleaning. 
  • Additionally, because tube is closed off from the outside environment, air currents and effects due to changing temperatures are removed and no longer an issue. The results is that images are clearer, steadier and sharper than those from a reflector telescope of the same size.


Disadvantages


  1. All refractors suffer from an effect called chromatic aberration (``color deviation or distortion'') that produces a rainbow of colors around the image. Because of the wave nature of light, the longer wavelength light (redder colors) is bent less than the shorter wavelength light (bluer colors) as it passes through the lens. This is used in prisms to produce pretty rainbows, but can it ruin an image! There a couple of ways to reduce chromatic aberration. One way uses multiple compensating lenses to counteract chromatic aberration. The other way uses a very long objective focal length (distance between the focus and the objective) to minimize the effect. This is why the early refracting telescopes were made very long.
  2. How well the light passes through the lens varies with the wavelength of the light. Ultraviolet light does not pass through the lens at all.
  3. The thickness of the objective lens has a direct effect on how well light passes through it.  The amount of light decreases as the thickness of the lens increases.
  4. It is extremely difficult and expensive to manufacture a glass lens with no imperfections inside the lens, that also has a perfect curvature on both sides of the lens. As a result, less expensive refracting telescope often contain an inferior objective lens which results in distorted images.
  5. By design, an objective lens is only supported only at the edges. Unfortunately overtime, the glass of the lens will sag under its own weight resulting in image distortion.


A refracting telescope is a great tool for anyone to use for viewing the sky above. Their sturdy construction is resistant to misalignment, and they generally require relatively simple maintenance. 


Be sure to check out our comprehensive Telescope 101 Guide for more information about all aspects of telescopes, including history, construction, components, plus care and maintenance tips.


What Is It

The refracting telescope (also called a refractor) is a special type of telescope that is characterized by it'a long, straight tubular body.  It is uses a large lens at one end of the tube to capture light from the image being viewed, while the viewer is positioned at the opposite end with an smaller lens (eyepiece).


History

Although the exact inventor of the refracting telescope is not known, Hans Lippershey is generally credited with the creation of the telescope due to the fact that he was the first person known to have documented a written record of the device as part of a patent that he filed in the year 1608.


Throughout history there have been many famous astronomers and scientists that have made significant contributions to astronomy thanks in part to the functionality of the refracting telescope.


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