Each side of each piece is ground and polished, and then the two pieces are assembled together. There telescope. The era of the 'great refractors' in the 19th century saw large achromatic lenses, culminating with the largest achromatic refractor ever built, the Great Paris Exhibition Telescope of 1900. , The telescope used for the discovery was the 26-inch (66 cm) refractor (telescope with a lens) then located at Foggy Bottom. Telescope, device used to form magnified images of distant objects. inverted image) or a convex objective and concave eyepiece lens (that would produce upright image). If a lens is convex or converging, it takes parallel light rays from a distant object and bends them so that they converge to a single point called the focal point. If a lens is concave or diverging, it takes parallel rays and bends them so that they spread out. , One of the famous triplet objectives is the Cooke triplet, noted for being able to correct the Seidal aberrations. In the 18th century, Dollond, a popular maker of doublet telescopes, also made a triplet, although they were not really as popular as the two element telescopes.  The breakthrough in glass making techniques led to the great refractors of the 19th century, that became progressively larger through the decade, eventually reaching over 1 meter by the end of that century before being superseded by silvered-glass reflecting telescopes in astronomy. This allows for a much wider field of view and greater eye relief, but the image for the viewer is inverted. Nevertheless, the astronomical community continued to use doublet refractors of modest aperture in comparison to modern instruments. Lippershey’s In any case, in 1608 he managed to create first crude telescope that had either two convex lenses (that produced Even though the managed to be quicker than one another lens maker In that Galileo Galilei's discovered the Galilean satellites of Jupiter in 1610 with a refracting telescope. , Jupiter's moon Amalthea was discovered on 9 September 1892, by Edward Emerson Barnard using the 36 inch (91 cm) refractor telescope at Lick Observatory. telescope had a modest three-times magnification, and Galileo managed to craft 10 times more powerful one. They are designed to bring three wavelengths (typically red, green, and blue) into focus in the same plane. Lenses form images by refraction and are typically made of either glass or plastic. The ratio β/α is called the angular magnification. The combination of an objective lens 1 and some type of eyepiece 2 is used to gather more light than the human eye is able to collect on its own, focus it 5, and present the viewer with a brighter, clearer, and magnified virtual image 6. List of the largest refracting telescopes, Albert Van Helden, Sven Dupré, Rob van Gent, The Origins of the Telescope, Amsterdam University Press, 2010, pages 3-4, 15. wanted to take credit for. One of the more famous applications of the refracting telescope was when Galileo used it to discover the four largest moons of Jupiter in 1609. Apochromatic refractors have objectives built with special, extra-low dispersion materials. report it was described how watch-maker and master lens-grinder Hans Lippershey has managed to combine specially crafted lenses to create first working Many early discoveries of the Solar System were made with singlet refractors. and Italian Galileo Galilei who managed to build a significantly more powerful telescope in a month of hearing about Hans Lippershey’s design. Considerably higher magnifications can be reached with this design, but to overcome aberrations the simple objective lens needs to have a very high f-ratio (Johannes Hevelius built one with a 46-metre (150 ft) focal length, and even longer tubeless "aerial telescopes" were constructed). However, the first successful refracting telescope came in … A 100 mm (4 in) f/6 achromatic refractor is likely to show considerable color fringing (generally a purple halo around bright objects). Some famous 19th century doublet refractors are the James Lick telescope (91 cm/36 in) and the Greenwich 28 inch refractor (71 cm).