Achromatic Refracting Telescope

Refracting telescope gadgets have what is called the chromatic aberration problem. Because glass tends to refract any light differently in terms of wavelength, the telescope lens will break light coming in into varied colors which is a similar concept to the prism. Consequently, this effect limits the use of the refracting telescope because the overall effect would be a blurred image.

Chromatic aberration will be more pronounced and worse if you would attempt to assemble a telescope with a low focal ratio or large aperture. The ancient astronomers were aware of this and so they created lengthy focal ratio refractors with small aperture.

Christian Huygens, in the year 1656, was able to construct a refractor possessing a 2 to 4 inch aperture and a 23 foot focal length. This refracting telescope was able to magnify around a hundred times and had a view field of around 16-17 arc minutes. On the other hand, in order to gain better magnification, Johannes Hevelius did construct a 140 foot telescope in 1670.

Significant advancement of the refracting telescope happened in the invention of the achromatic objective. Although someone as prominent as Isaac Newton said that achromatic objectives are not possible, he was proven to be wrong when a British optical maker, John Dolland invented an achromatic lens using two types of glass which can provide better quality correction of color than the simple objectives.

The modern refracting telescopes now utilize the achromatic lens. Normally achromatic lens use two to three glass types having varied dispersions. This means that the light is spread into the spectrum differently. There is careful balance on the lens power, thereby reducing significantly the color effors. Ultimately the refracting telescopes that have large aperture and high focal lengths are much more feasible.

On the Optical Telescope

Optical telescope is defined as a telescope that collects light and focuses it primarily from the spectrum’s visible portion to make a direct view of a magnified or enlarged image, or taking a photograph among others.

If you know or have seen a monocular, then optical telescope is another term for it. Monoculars are optical gadgets that have state mount used in the sky gazing and observing. On the other hand, binoculars are especially for other gazing and observing purposes.

There are three major types of the optical telescope – the refracting telescope, which utilize its lenses, the reflecting telescope, which uses mirror, and the mirror-lens system, which as the name suggest makes use of both mirrors and lenses. Example of a refracting telescope is the earliest scope, the popular Galileo telescope. Examples of the mirror lens system are the Schmidt camera and Maksutov scope.

The Hubble Space Telescope is another optical telescope that is perhaps the most popular telescope today. It is circling an orbit past the atmosphere of the Earth for it to gather observations that are clear of atmospheric elements. With the Hubble Space Telescope, the images can be limited in diffraction, and the coverage is in infrared and ultra-violet rays. Another popular optical telescope is the Keck telescope, which is said to be one of the largest scopes in the world.