Windows on the Universe: Refracting Telescopes

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How It Works- Refracting telescopes use two glass lenses to gather and focus light. They bend, or refract light as their name suggests, as it passes through different mediums. The objective lens gathers and then refracts it to a focus near the end of the tube. The image is magnified and brought to the viewer’s eye by the eyepiece. Information It Provides- Optical telescopes are used to observe objects, which are in the visible light spectrum, by magnifying the image and thereby improving the detail. It provides information, such as appearance and motion, on celestial bodies which would otherwise be too difficult to see with the unaided human eye. Advantages and Disadvantages Advantages Disadvantages High contrast images as there is no secondary mirror which obstructs some light Lenses are expensive and time-consuming to manufacture Closed tube protects optics from dust, moisture, light and air currents which degrade the image The amount of refraction on the lens depends on the wavelength so different wavelengths focus at slightly different places. This is chromatic aberration, a problem where a rainbow halo appears around images. Needs little maintenance. It is more resistant to misalignment than the reflecting telescope Heavier, longer and bulkier than other telescope types Optical Telescopes- Reflecting- Ground Based Example- W.M. Keck Observatory (Hawaii, US) How It Works- Instead of using lenses to gather light, these telescopes use concave, primary mirrors at the

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