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


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 instruments 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 Newtons 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 telescopes tube? Gregorys 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 telescopes outer tube and bringing
the image out by placing a small, flat metal mirror at an angle of 45° to the
telescopes 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. Newtons 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)