Here is a list of the largest optical refracting telescopes sorted by lens diameter. The largest refractor ever constructed was French. It was on display at the 1900 Paris Exposition. Its lens was stationary, prefigured so as to sag into the correct shape. The telescope was aimed by by the aid of a Foucault sidérostat, which is a movable plane mirror of diameter 6.56 feet, mounted in a large cast-iron frame. The horizontal tube was 197 feet long and the objective had 4.1 feet in diameter. The results were poor. When the year-long exposition was over, its builders were unable to sell it. It was ultimately broken up for scrap.


           
             
             
             
             
             
             
             
             
             
             
             
             
             
             
             

Observatory

Lens diameter

Focal length

Built

Comments

Paris 1900 Exposition
(Paris, France)

1.25 m

57 m

1900

 Fixed lens, total failure.

Yerkes Observatory
(Williams Bay, Wisconsin, USA)

1.02 m

19.4 m

1897

 

Lick Observatory
(Mount Hamilton, California, USA)

0.91 m

17.6 m

1888

 

Paris Observatory
(Meudon, France)

0.83 m + 0,62 m

16.2 m

1891

Double telescope

Potsdam Observatory
(Potsdam, Germany)

0.80 m

12.0 m

1899

 

Côte d'Azur Observatory
(Nice, France)

0.76 m

17.9 m

1887

 

Allegheny Observatory
(Pittsburgh, Pennsylvania, USA)

0.76 m

14.1 m

1914

 

Royal Greenwich Observatory
(Greenwich, London, England)

0.71 m

8.5 m

1894

 

Vienna Observatory
(Vienna, Austria)

0.69 m

10.5 m

1878

 

Berlin Observatory
(Berlin, Germany)

0.68 m

21 m

1896

 

Johannesburg Observatory
(Johannesburg, South Africa)

0.67 m

10.9 m

1925

 

McCormick Observatory
(Mount Jefferson, Virginia, USA)

0.67 m

9.9 m

1883

 

Royal Greenwich Observatory
(Greenwich, London, England)

0.66 m

6.8 m

1897

 

U.S. Naval Observatory
(Washington, DC, USA)

0.66 m

9.9 m

1873

 

Mount Stromlo Observatory
(Mount Stromlo, Australia)

0.66 m

10.8 m

1925

Previously located in South-Africa.
Relocated in Australia in 1952
Destroyed by bush fire on January 18, 2003