Alvan Clark didn't know anything about telescopes when, in 1844, his son George made one out of the melted-down brass of his school's broken dinner bell. But the elder Clark was soon hooked on a new hobby, one at which the established portrait painter apparently excelled. He began making refractor telescopeswhich use paired lenses to focus lightand taught himself to be a master optician, able to spot even the tiniest imperfections in the glass objectives he crafted.
His two sons, George Bassett Clark and Alvan Graham Clark, joined their father's growing business, and together they founded the firm of Alvan Clark and Sons, makers of the finestand largestrefractor telescopes of their time. Before they were done, the Clarks had five times created lenses for the world's largest telescopes, often beating their own records.
Through Clark telescopes, scientists have discovered the spiral arms of our own galaxy, the moons of Mars, the fifth moon of Jupiter. The first evidence of an expanding universe, the observation that other galaxies are moving away from us, was found with a Clark refractor.
Today, refractors have been largely eclipsed for research use by reflector telescopes. (Barrel-shaped as opposed to long and lean, these telescopes use mirrors to focus light.) But the Clark refractorsfrom the 40-inch at the Yerkes Observatory (the world's largest, completed months before the youngest Clark's death in 1897) to the hundreds of smaller models, cherished by collectorsremain elegant reminders of a golden age of astronomy, and one family's dedication to its craft.