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Optical telescopes can be classified by three primary optical designs (refractor, reflector, or catadioptric), by sub-designs of these types, by how they are constructed, or by the task they perform. They all have their different advantages and disadvantages and they are used in different areas of professional and amateur astronomy .
Lens sag is a problem that sometimes afflicts very large refracting telescopes. It is the equivalent of mirror sag in reflecting telescopes. It occurs when the physical weight of the glass causes a distortion in the shape of the lens because the lens can only be supported by the edges. A mirror on the other hand can be effectively supported by ...
The Swedish 1-m Solar Telescope, with a lens diameter of 43 inches, is technically the largest, with 39 inches clear for the aperture.The second largest refracting telescope in the world is the Yerkes Observatory 40 inch (102 cm) refractor, used for astronomical and scientific observation for over a century.
A refracting telescope (also called a refractor) is a type of optical telescope that uses a lens as its objective to form an image (also referred to a dioptric telescope). The refracting telescope design was originally used in spyglasses and astronomical telescopes but is also used for long-focus camera lenses .
This is a list of large optical telescopes. For telescopes larger than 3 meters in aperture see List of largest optical reflecting telescopes . This list combines large or expensive reflecting telescopes from any era, as what constitutes famous reflector has changed over time.
A reflecting telescope by James Short; this English telescope maker produced almost 1400 Gregorian reflectors in the mid-1700s. Mobile versions were used to observe the Transit of Venus . List of largest optical telescopes in the 18th century includes various refractors and reflectors that were active some time between about 1699 to 1801.
Henry Draper with a refractor telescope set up for photography (photo probably taken in the 1860s or early 1870). [ 2 ] The development of astrophotography as a scientific tool was pioneered in the mid-19th century for the most part by experimenters and amateur astronomers , or so-called " gentleman scientists " (although, as in other ...
A 12-inch refractor was moved to Yerkes from Kenwood Observatory in the 1890s. [13] Two other telescopes planned for the observatory in the 1890s were a 12-inch aperture refractor and a 24-inch reflecting telescope. [13] There was a heliostat mirror and a meridian room for a transit instrument. [13]