ppears blurred and discolored. There is no such difficulty with a mirror, because there is in that case no refraction of the light, and consequently no splitting up of the elements of the spectrum.
In order to get around the obstacle formed by chromatic aberration it is necessary to make the object glass of a refractor consist of two lenses, each composed of a different kind of glass. One of the most interesting facts in the history of the telescope is that Sir Isaac Newton could see no hope that chromatic aberration would be overcome, and accordingly turned his attention to the improvement of the reflecting telescope and devised a form of that instrument which still goes under his name. And even after Chester More Hall in 1729, and John Dollond in 1757, had shown that chromatic aberration could be nearly eliminated by the combination of a flint-glass lens with one of crown glass, William Herschel, who began his observations in 1774, devoted his skill entirely to the making of reflectors, seeing no pro
Is The Iron Eagle a psychotic serial killer?
When everyone reads minds, a secret is a danger... Read more
In the fall of 1984, Cold War tensions between... Read more
Author Al Macy is a character and a tightwad wi... Read more
The list of books below is based on the weekly downloads by our users regardless of eReader device or file format.
See more popular titles from this genre.