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leehom
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Why do very large astronomical telescopes use a mirror rather than a lens for the objective optic?
Astronomical telescopes use mirrors instead of lenses because mirrors can gather and focus light over a larger area, resulting in a brighter and clearer image. Lenses, on the other hand, can only gather and focus light at their edges, resulting in a dimmer and less sharp image.
The curved shape of the mirror in a telescope allows it to reflect light and direct it towards a focal point, where an eyepiece or camera can then gather the light and create an image. The larger the mirror, the more light it can gather, resulting in a brighter image.
The main advantage of using mirrors in telescopes is their ability to gather and focus more light, resulting in a clearer and brighter image. Additionally, mirrors are easier to manufacture and maintain compared to lenses, and they are not affected by chromatic aberration, which can distort images in lenses.
The use of mirrors in telescopes can result in a phenomenon called spherical aberration, where the edges of the mirror do not focus light as accurately as the center. This can be corrected by using a parabolic shape for the mirror or adding additional mirrors to the telescope design.
Yes, lenses can be used in astronomical telescopes, but they are typically only used in smaller, more portable telescopes. Lenses have a limited ability to gather light and can distort images due to chromatic aberration, making them less ideal for larger and more precise telescopes used in astronomy.