Two of them measure 49 inches (1.25 meters) in diameter.
These lens were once the most critical components of the largest refracting telescope ever attempted.
The Great Telescope, installed, from the ocular lens end.
The centerpiece of Exposition Universelle was the Great Paris Exhibition Telescope housed inside Palais de l’Optique.
Because of their enormous size and weight, the telescope couldnt be maneuvered to aim at astronomical objects.
The telescopes eyepiece was placed on rails and could be shifted by five feet for focusing.
With the lowest power of 500, the telescope had a field of view of 3 arc minutes.
In the end, the telescope turned out to be largely a gimmick and not a serious astronomical instrument.
During the fair, thousands of people came to watch the telescope.
They paid a few cents and peered through the eyepiece.
But not a single buyer came forward.
Still, no one bought it.
The eye-piece holder
An 1892 cartoon ridiculing Francois Deloncles proposal to “bring the moon within a meter”.
Sources:Wikipedia/Unusual Telescopes by Peter L. Manly/Gale/Arthur Chandler
