Newton fashioned a concave mirror from a mixture of copper and tin, which gives a surface with almost the luster of silver. An image of the star was produced in the focus of this mirror, and then this image, when examined by a magnifying eyepiece, permits the astronomer to study the star at what is equivalent to a greatly reduced distance. Such is the principle of the famous erecting telescope which bears the name of Newton.
The little reflector which he constructed is still preserved as one of the treasures of the Royal society. The telescope tube had the very modest dimensions of an inch in diameter. It was, however, the precursor of a whole series of magnificent instruments, each outstripping the other in magnitude, until at last the culminating point was attained in the construction of Lord Rosse's mammoth reflector of 6 feet in aperture. — Good Words.
Friday, July 11, 2008