Early
Telescopes and Their Limitations
- Early telescopes were hard to make because it was difficult to grind and polish the lenses and also because of the low quality of glass then available.
- Galileo built about 100 telescopes and he only
considered 10 of them to be any good.
- They had limited magnification.
- About 30x for Galileo's telescopes.
- They had a small field of view which is the amount of
sky you can see at one time.
- Galileo's telescopes at about 20x could only see
about a quarter of the moon.
- They suffered from spherical aberration -- aberration
just means different than expected.
- Spherical aberration is caused because light rays
that go through the center of a spherical lens focus in a
different place than the light rays that go through the
edges of the lens. It thus makes the image fuzzy instead
of being focused and clear because of the many focal
points.
- They suffered from chromatic aberration.
- Chromatic aberration is when a fringe of color
appears around a bright object and this is because
different colors of light focus at different points when
they go through a glass lens.
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Spherical
Aberration
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Chromatic
Aberration
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