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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.
Seeing is a major limitation to the angular resolution in astronomical observations with telescopes that would otherwise be limited through diffraction by the size of the telescope aperture. Today, many large scientific ground-based optical telescopes include adaptive optics to overcome seeing.
The diffraction-limited angular resolution, in radians, of an instrument is proportional to the wavelength of the light being observed, and inversely proportional to the diameter of its objective's entrance aperture. For telescopes with circular apertures, the size of the smallest feature in an image that is diffraction limited is the size of ...
This list of the largest optical reflecting telescopes with objective diameters of 3.0 metres (120 in) or greater is sorted by aperture, which is a measure of the light-gathering power and resolution of a reflecting telescope. The mirrors themselves can be larger than the aperture, and some telescopes may use aperture synthesis through ...
Ultimately, a valid comparison between two telescopes must take into consideration more specifications, when a general measurement becomes obtuse. Aperture of the primary mirror alone can be poor measure of a reflective telescope's significance; for example, the Hubble Space Telescope has only a 2.4 metres (94 in) primary mirror. In addition ...
Dawes' limit is a formula to express the maximum resolving power of a microscope or telescope. [1] It is so named after its discoverer, William Rutter Dawes, [2] although it is also credited to Lord Rayleigh. The formula takes different forms depending on the units.
The plate scale of a telescope connects the angular separation of an object with the linear separation of its image at the focal plane. If focal length is measured in mm, the plate scale in radians per mm is given by angular separation θ and the linear separation of the image at the focal plane s, or by simply the focal length f:
People flock to the new David Dunlap Observatory in the 1930s, the second largest reflecting telescope in the world going by a mirror diameter of 74 inches (about 1.9 meters) at that time. Telescopes have grown in size since they first appeared around 1608. The following tables list the increase in size over the years.