ester Moore Hall in 1733
-The design overcame the need for very long focal lengths in refracting telescopes by using an objective made of two pieces of glass with different dispersion, "crown" and "flint glass", to limit the effects of chromatic and spherical aberration.
-Chromatic aberration is a type of distortion in which there is a failure of a lens to focus all colours to the same convergence point.
-Spherical aberration is an optical effect observed in an optical device that occurs due to the increased refraction of light rays when they strike a lens or a reflection of light rays when they strike a mirror near its edge, in comparison with those that strike nearer the centre.
-Apochromatic refractors have objectives built with special, extra-low dispersion materials.
-They are designed to bring three wavelengths (usually red, green, and blue) into focus in the same plane.
-Such telescopes contain elements fluorite or special, extra-low dispersion (ED) glass in the objective and produce a very crisp image that is virtually free of chromatic aberration.
BENEFITS TO THE SOCIETY AND THE ENVIRONMENT
Refracting telescopes find a wide range of applications in astronomy, though the applications include non-astronomical uses as in binoculars and cameras. Refracting telescopes make use of lenses. They usually focus the light waves with the help of these lenses.
Telescopes are one of the main ways that astronomers explore the universe. Refracting telescopes gather more light and better resolution. Resolution is the ability of a telescope to bring distant object close together: for an example the ability to clearly separate two stars that are very close together or the ability to see smaller craters on the moon.
Telescopes are used in stargazing and amateur astronomy. Lots of astronomical research is done on telescopes that look at other wavelengths of light. Each of these wavelengths ranges shows us something unique about universe and allow us to view events and objects that can't be seen with human eyes.
Astronomers study objects in space with the use of telescopes. This helped them to make observations to find amazing discoveries.