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This article is a list of notable unsolved problems in astronomy. Problems may be theoretical or experimental. Theoretical problems result from inability of current theories to explain observed phenomena or experimental results. Experimental problems result from inability to test or investigate a proposed theory.
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 ...
Recent examples of this telescope have sold for well into 5 figures. Today, Tele Vue's apochromatic refractor telescopes, which have reduced chromatic aberration, come in diameters ranging from 60mm (2.4 inches) to 127mm (5 inches). [1] The imaging system ("is" series) telescopes are designed primarily for astrophotography.
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 .
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.
Then with the discovery of optics, with the help of different types of refractor telescopes and later with reflector telescopes. Their use allowed to dramatically increase both the collecting power and limit of resolution , thus the brightness , level of detail and apparent angular size of distant celestial objects allowing them to be better ...
Although diffraction spikes can obscure parts of a photograph and are undesired in professional contexts, some amateur astronomers like the visual effect they give to bright stars – the "Star of Bethlehem" appearance – and even modify their refractors to exhibit the same effect, [5] or to assist with focusing when using a CCD.
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.