Digital Access to a Sky Century @ Harvard

The Digital Access to a Sky Century @ Harvard (DASCH) was a project that digitized much of the collection of astronomical photographic glass plate negatives created by the Harvard College Observatory and housed in the collection known as the Harvard Plate Stacks. It was a major project of the Center for Astrophysics | Harvard & Smithsonian. The project digitized nearly all of the direct images in the Harvard Plate Stacks with a total of 429,274 glass plates scanned for the final data release in 2024. The database contributes to the field of time domain astronomy, providing nearly hundred years more 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. The scope of the Harvard Plate Stacks collection is unique in that it covers the entire sky for a very long period of time.