Some name that person as Hans Lippershey (c. Leonard Digges is sometimes credited with the invention in England in the 1570s, but usually credit for assembling the first telescope is given to an unknown Dutch spectacle maker in about 1608. The first telescopes may have been Assyrian crystal lenses, but the Visby lenses tentatively suggest that the technology was known to the Arabs and Persians. High energy particle telescopes detect a flux of particles, usually originating at an astronomical source.Ī replica of the first telescope built and used by Galileo, on display at the Griffith Observatory The mirrors are usually a section of a rotated parabola. They use ring-shaped "glancing" mirrors, made of heavy metals, that reflect the rays just a few degrees. X-ray and gamma-ray telescopes have a problem because these rays go through most metals and glasses. Aperture synthesis is now also being applied to optical telescopes using optical interferometers (arrays of optical telescopes) and Aperture Masking Interferometry at single telescopes. As of 2005, the current record array size is many times the width of the Earth, utilizing space-based Very Long Baseline Interferometry (VLBI) telescopes such as the Japanese HALCA (Highly Advanced Laboratory for Communications and Astronomy) VSOP (VLBI Space Observatory Program) satellite. Multi-element Radio telescopes are constructed from pairs or larger groups of these dishes to synthesize large "virtual" apertures that are similar in size to the separation between the telescopes: see aperture synthesis. The dishes are sometimes constructed of a conductive wire mesh whose openings are smaller than a wavelength. Single-dish Radio telescopes are focusing radio antennae often having a parabolic shape. Optical telescopes are used for astronomy and in many non-astronomical instruments including theodolites, transits, spotting scopes, monoculars, binoculars, camera lenses and spyglasses. Telescopes work by employing one or more curved optical elements - lenses or mirrors - to gather light or other electromagnetic radiation and bring that light or radiation to a focus, where the image can be observed, photographed or studied. Telescopes increase the apparent angular size of distant objects, as well as their apparent brightness. The term usually refers to optical telescopes, but there are telescopes for most of the spectrum of electromagnetic radiation and for other signal types.Īn optical telescope gathers and focuses visible light and other electromagnetic radiation. As a result, telescopes at other wavelengths either view changes on spatial scales larger than those observed with the EHT, or have a difficulty in discerning where exactly (with respect to the black hole) the changes are happening.50 cm refracting telescope at Nice Observatory.Ī telescope (from the Greek tele = 'far' and skopein = 'to look or see' teleskopos = 'far-seeing') is an instrument designed for the observation of remote objects. Other radio arrays, including global ones like the GMVA, do not operate at short enough wavelengths, while at wavelengths shorter than about a tenth of a millimeter long-distance interferometry becomes technically impossible. Resolving power scales directly with the observing wavelength and inversely with the distance between the furthest telescopes in an interferometric array such as the EHT. Only observations with the Earth-sized EHT array at wavelength below approximately 2 mm have the theoretical resolving power sufficient to discern the very small size of the event horizons of black holes in SgrA* and M87. What makes the radio observations at 1 mm wavelength different from observations in any other wavelength band is the spatial resolution. A number of optical and infrared telescopes monitored the EHT targets, as did X-ray telescopes Chandra, Swift, NuSTAR, and AstroSat, and high-energy gamma-ray observatories MAGIC, VERITAS, and HESS. In 20, coordinated observations were performed by various radio telescope arrays operating at wavelengths longer than 1 mm, such as GMVA, VLBA, KVN, HSA, EVN, RadioAstron. The aim of this is to provide multi-wavelength coverage in order to investigate potential correlations in source brightness in various bands across the electromagnetic spectrum. Scientists of the EHT and their collaborators try to organize observations with a number of different telescopes so that they coincide with observations with EHT observations.
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