Nobody has ever systematically looked at the sky on 100-year time scales, said Josh Grindlay, the Harvard astronomer in charge of the project. There is this whole dimension that hasn’t been explored.

The Harvard Observatory holds more than a century of astronomical records. Below (picture 1), we can see cabinets filled with photographic plates in 1891.

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The great Refractor (below), which in 1850 captured the first picture of a star; images from the archives, including the Large Magellanic Cloud (1900), the constellation Sagittarius (1943) and the Rho Ophiuchus nebula (1948)

In 1889 when this was still an analog world, a young astronomer named Solon I. Bailey carefully packed two crates of glass photographic plates taken at his outpost in the Peruvian Andes for shipment to Harvard College Observatory. Carried down the mountain on mule back and across a suspension bridge to the village of Chosica, the fraile load was put on a train bound for Lima and the long voyage to Boston Harbor.

For nearly 18 months the data stream continued -more than 2,500 plates from what Mr. Bailey had quaintly named Mount Harvard- followed in the coming years by tens of thousands more from a second Peruvian station in Arequipa.

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The “computer” room at the Harvard Observatory in 1891, below, where women examined glass photographic plates containing images of the sky. One of their most important tasks was looking for stars that changed periodically in brightness. (Picture 3)

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The reliance on photographic plates continued until the mid-1980s when electronic imaging came of age. The eyes of the astronomers were replaced by charge-coupled devices, or C.C.D., allowing for faster, more voluminous observations with all the advantages of a searchable database.

Today, Picture 4 below, Alison Doane, curator of the glass database, compares a chart with a glass plate in her office.

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Below, an observatory camera from 1891 (picture 5), and the custom-built scanner now used to digitalize the old plates, shown in binders at picture 6, is the handwritten logbooks, which researchers are working to transcribe.

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* Summarized and adapted from New York Times, July 10, 2007