List of largest optical telescopes in the 18th century


List of largest optical telescopes in the 18th century, are listings of what were, for the time period of the 18th century, large optical telescopes. The list includes various refractor and reflector that were active some time between about 1699 to 1801. It is oriented towards astronomy, not terrestrial telescopes.
Many of the largest were metal mirror reflectors, some of which had substational apertures even for the 20th century. One problems was that many instrument makers including Herschel did not pass on their mirror making craft, and by the next century reflectors had largely been passed over in favour of small achromats. It was not until the 21st century that really large refactors would predominate once again. Some of the achievements in astronomy of the 19th century telescopes include the discovery of the planet Uranus, the Messier catalog, and overall increased detections of comets, stars, star catalogs, and other charting.
The major breakthrough in the 1700s, was the discovery of two and even three lens telescopes and increased spread of reflecting telescopes and their designs. In this period reflectors used metal mirrors not metal coated class, which was not pioneered until the next century.

Selected Reflectors & Refractors

The main telescope technologies during this period were refractors with non-achromatic objectives, speculum metal reflectors, refractors with achromatic doublets objective, and apochromatic triplets objectives. The list is inherently limited by what examples and records survived.


Legend



NameAperture
cm 		TypeSignificanceLocation then/Original SiteExtant*
Herschel 40-foot 126 cmReflectorWorld's largest 1789;
Mimas & Enceldaus discovery telescope		Observatory House; England1789–1815
Rev John Michell's Gregorian reflector75 cm Reflector - GregorianWorld's largest 1780Yorkshire, Great Britain1780–1789
Herschel "X Feet" or "Large 10 Feet"61 cm ReflectorEngland1800
Father Noel's Gregorian reflector60 cm Reflector - GregorianWorld's largest 1761; 1796 Newtonian conversionParis, France1761-1841
James Short Gregorian reflector50 cm Reflector - GregorianWorld's largest 1750Scotland1750
Schröter 27 foot Newtonian47 cm ReflectorLilienthal, Lower Saxony 1793-1813
Herschel 20-foot47 cm ReflectorObservatory House; England1782
James Short Reflector for King of Spain46 cm Reflector - GregorianSpain1752
James Short's Gregorian reflector38 cm Reflector - GregorianWorld's largest 1734Scotland1734
Huygens aerial for Royal Society of London19 cm aerialLondon, England1691-1786
William Herschel 7-foot16 cm ReflectorDiscovered Georgium SidusEngland1776–1783
Hadley's Reflector15 cm ReflectorFirst parabolic newtonianEngland1721
Van Deyl of Amsterdam telescope11.4 cm achromatEngland1781
James Short 4.5 inch reflector11.4 cm reflectorEngland1737
Shuckburgh telescope10 cm achromatFirst large equatorialWarwickshire, England1791–1923
Dollond Apochromatic Triplet9.53 cm apochromatFirst apochromatic tripletEngland1763
Dollond Triplet for Wollaston9.02 cmtriple lensRAS No. 16England1771
Francesco Bianchini's aerial telescope6.6 cm aerialRome, Italy1726
Chester Moore Hall's Doublet6.4 cm achromatFirst achromatic doubletEngland1733
Troughton Equatorial Telescope5.08 cm achromatEquatorial mountArmagh Observatory, Ireland1795
Newton's reflector 3.3 cm ReflectorFirst reflecting telescopeEngland1668-1704

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