The refracting telescope is the earliest instrument used for serious astronomical study and has earned a very important place in the history of astronomy.
From the earliest Galileo telescope and the simple refractor telescope of Hans Lippershey, to the modern refractor – this device is by far one of the most prolific when it comes to astronomical discoveries.
It is also one of the simplest; anyone can build a refractor telescope following its basic principle. You can assemble a simple scope if you have in hand any long tube and two lenses, which would act as the eyepiece and objective lenses.
This is as opposed to the reflecting telescope. Instead of objective lens and eyepiece, basically mirrors for gathering and magnifying light are used by the reflecting telescope.
Indeed, the refractor is an efficient instrument used for viewing distant objects such as planets or even stars.
However, the refracting telescope is a flawed instrument.
Have you heard of chromatic aberration? It is an optic occurrence wherein different wavelengths of lights that pass through a lens are caused to likewise have different focal lengths. And since every color of the spectrum can’t be focused at a common point of the optical axis, the image is surrounded with colors.
This optical defect is minimized, if not corrected, by using achromatic optics or doublets. These achromats are equipped with materials that are bonded to form one lens. This in turn helps in minimizing the degree of chromatic aberration.
Many glass materials are being utilized in minimizing chromatic aberration. Glass containing fluorite are said to be the best in reducing this optical defect in refracting telescope.
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