Today in Technology History
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July 10
The world's largest refracting telescope was built by a Alvan Graham Clark, an American astronomer born exactly 170 years ago.
Clark was born in Massachusetts on July 10, 1832. When he was young he painted portraits for a living -- but he eventually started working for his father, an instrument maker. Clark's father had started selling astronomical lenses in the 1840s and his firm's reputation and business had grown rapidly. The Clarks pioneered new techniques for producing astronomical lenses, including a remarkable method of using just their fingertips to gently correct lens imperfections.
Although most of Clark's life was spent working on the technology of astronomy, he also made one scientific discovery of significance: while testing a telescope he was making for a client, he looked at the star Sirius and caught the first glimpse of its companion star, a discovery which earned Clark a medal. Astronomers around the world used Clark-built telescopes to make other important discoveries.
Although the Clark family produced many small telescopes of high quality, they also provided big lenses. Again and again they set records for making the world's largest telescopes. In 1897, Clark produced 40-inch lenses for use in a gigantic telescope at the Yerkes Observatory in Wisconsin. For more than a decade, that telescope was the largest in the world; today, it remains the world's largest refracting telescope. (There are reflecting telescopes which are bigger; they are also easier to make.)
Soon after the installation of the lenses in the Yerkes telescope, Clark died -- one day before his 65th birthday.
Related links:
Click here and here to read short encyclopedia entries about Clark.
Click here and here to see pictures of the 40-inch Yerkes telescope.
Click here and here to read about a book that discusses the Clark family business.
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