The primary mirror, at the bottom of the telescope tube, curved inward slightly, in a spherical shape. Instead of glass lenses, Newton’s telescope used two polished metal mirrors. So Newton devised a new type of telescope, which he presented to his colleagues in England’s Royal Society in January 1672. Newton's mirror was made not of glass, but of a metal alloy consisting of three parts copper and one part tin, mixed with a small amount of arsenic, which would make the metal easier to polish. Any glass lens acts like a prism, splitting a beam of light into its individual wavelengths or colors, so there was no way to eliminate the colored haloes with lens-based telescopes.Ī replica of Isaac Newton's reflecting telescope. Isaac Newton, who is best known for devising his laws of motion and gravity, realized that part of the problem was with the glass itself. And the glass contained chemical impurities that colored the lenses green. Grinding glass to the right shape for refracting telescope lenses was a daunting task, and Galileo’s telescopes produced a slightly blurry view of the sky, with colored “haloes” around astronomical objects. (If you extend the curve of a parabolic surface into space it remains open, with the ends never joining.) James Gregory proposed this design in 1663, but there was no way to create parabolic mirrors at the time, so the design was not implemented for decades. Eventually, astronomers would adopt designs using mirrors with parabolic mirrors instead of spherical ones. While Newton’s reflecting telescope overcame the rainbow-like haloes around astronomical objects, it left the view somewhat distorted because of the mirror’s spherical curvature.
Calculated the color-distortion effects of refractive lenses.
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