Учебно-методическое пособие по чтению специальной литературы для студентов 1 курса физического факультета. Дроздова И.В - 15 стр.

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      mathematician, James Gregory, had suggested a plan for a reflecting telescope,
      but had never actually made one. Also, Gregory was not acquainted with such
      an instrument’s main advantage, namely that it would do away with the
      troublesome colour fringes.

8.    Isaac began shaping, with his own hands, the tiny metal mirror for the first
      reflecting telescope. Days were spent in polishing its concave surface. The
      alloy from which it was formed was Newton’s own – a mixture of copper, tin,
      and arsenic.

9.    Isaac worked with intense enthusiasm. The telescope he finally produced was
      ridiculously small. It was six inches long, with a diameter of one inch. Yet it
      could magnify an object forty times – and this, as Newton himself pointed out,
      was as much as could be expected of a refracting telescope fully six feet long.

10.   Yet Newton faced a new problem in making his telescope. James Gregory had
      suggested a reflecting instrument made up of two concave mirrors facing one
      another. Light from the object to be observed was to be reflected from one of
      them to a focal point in front of the other. But how could an observer see the
      image unless his head was inside the telescope’s tube? Gregory’s idea was to
      have the second mirror reflect the light again, and bring it to a focus through a
      hole drilled in the first mirror. Here the image could be seen by an observer
      using an eyepiece behind the hole.

11.   Newton realized that this was rather a clumsy arrangement. Instead, he hit on
      the idea of boring a hole in the side of the telescope’s outer tube and bringing
      the image out by placing a small, flat metal mirror at an angle of 45° to the
      telescope’s axis inside the telescope. Thus an observer using an eyepiece at the
      side of the instrument would catch the objects’ rays being thrown out
      sideways. Newton was the first man to use this device.

12.   Newton’s instrument was crude. The idea behind it was new. When he finished
      his telescope, Newton wondered how well it would work in practice. On the
      first clear night the young Trinity scholar turned it skyward and thrilled. There
      in the tiny eyepiece were the planet Jupiter and its then-known four moons.
      With a little difficulty and much practice Newton was also able to observe the
      phases of the planet Venus. And each of these images shone bright and clear
      and free from annoying colour fringes!

13.   Newton made this first reflecting telescope in the year 1668. Later in 1671, he
      was to make a second, which would win him fame and honour all over Europe.


                             Quiz (see appendix, keys)