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15
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)
15 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)
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