Digital Access to a Sky Century @ Harvard

The Digital Access to a Sky Century @ Harvard (DASCH) is a project to preserve and digitize images recorded on astronomical photographic plates created before astronomy became dominated by digital imaging. It is a major project of the Center for Astrophysics | Harvard & Smithsonian. Over 500,000 glass plates held by the Harvard College Observatory are to be digitized.^[1] The digital images will contribute to time domain astronomy, providing over a hundred years of data that may be compared to current observations.

From 1885 until 1992, the Harvard College Observatory repeatedly photographed the night sky using observatories in both the northern and southern hemispheres. Over half a million glass photographic plates are stored in the observatory archives providing a unique resource to astronomers. The Harvard collection is over three times the size of the next largest collection of astronomical photographic plates and is almost a quarter of all known photographic images of the sky on glass plates. Those plates were seldom used after digital imaging became the standard near the end of the twentieth century.^[2] The scope of the Harvard plate collection is unique in that it covers the entire sky for a very long period of time.