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Looking through Galileo's eyes

Modern astronomers marvel at what Galileo Galilei discovered with his 17th-century telescope.

The view from Galileo's last home now looks out on Italy's National Institute for Astrophysics, where researchers have made a model of his telescope. (Nicole Martinelli/GlobalPost)

[Editor's note: this story was updated to reflect the correct order of Galileo's full name — it is Galileo Galilei, not Galilei Galileo.]

ARCETRI, Italy — Astronomers have recreated Galileo Galilei’s telescope to celebrate the 400th anniversary of his groundbreaking observations.

Galileo spent his last eight years confined to Villa Gioiello here in the hills south of Florence after he was condemned as a heretic in 1632 for his conclusion that the Earth revolved around the sun. The small white building has a bare facade, except for a bust of the scientist staring fiercely at the Trattoria Omero across the street.

In the late 19th century, the white domes of the National Institute for Astrophysics (INAF) observatory rose within view of the Villa. Now, after two years of study, INAF researchers are observing the night sky with a replica of Galileo’s telescope.

They began trying to see through Galileo’s gaze in January 2009. While Galileo spent just one winter making his observations, researchers strung out the work over the year. Paolo Stefanini, a technician who has solved problems big and small at INAF since 1966, believes Galileo would recognize the simple metal tool he crafted.

“When we first set out to re-create it, aesthetics played a part,” Stefanini said. “But we also needed something sturdy. The original was made from strips of wood joined together and covered with red leather; we needed a telescope that could be used without falling apart.”

Like Galileo's instrument, the modern replica is about three feet long. It magnifies distant objects by refracting light through lenses housed in a tube, with a light-gathering objective lens at one end and an eyepiece at the other.

Stefanini made his refracting telescope and tripod from spare metal parts found around the observatory. The lenses were crafted by the National Institute of Applied Optics in Florence, which measured the shape and refractive index of the originals and the National Institute of Nuclear Physics in Florence, where scientists determined glass composition using X-ray fluorescence.

Instead of one man peering at the winter night sky and making hasty sketches, however, the images are recorded by a light-sensitive silicon chip called a charge coupled device or CCD. Attached to a digital camera, it transforms photons into electrical signals, making digital versions of the images as they would form on the retina of a human observer. Starry skies captured by the replica will be published online in early 2010.

Galileo wasn't the first to point a telescope at the heavens, but the 45-year-old-mathematics professor taught himself the art of lens grinding, making his the most powerful around.
His instrument magnified 20 times, allowing him to see moon craters, identify individual stars in the Milky Way and Jupiter's four largest moons.

Galileo spent late 1609 and early 1610 gathering information and drawing the sky; his observations became the Sidereus Nuncius (“Starry Messenger”) a treatise that led to a clash with the Inquisition.