Digital Access to a Sky Century @ Harvard
| DASCH | |
|---|---|
| Commercial? | No |
| Location | Cambridge, Massachusetts, United States |
| Owner | Harvard–Smithsonian Center for Astrophysics |
| Founder | Jonathan E. Grindlay, principal investigator |
| Country | United States of America |
| Established | 2001 |
| Funding | National Science Foundation |
| Status | Active |
| Website | dasch |
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 Harvard–Smithsonian Center for Astrophysics. Over 500,000 glass plates held by the Harvard College Observatory are to be digitized. 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 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 collection is unique in that it covers the entire sky for a very long period of time.
The project web site states that the goals of DASCH are to "enable new Time Domain Astronomy (TDA) science, including:"
Digitizing the Harvard College Observatory's astronomical plates archive was first considered in the 1980s by Jonathan E. Grindlay, a professor of astronomy at Harvard. Grindlay encouraged Alison Doane, then curator of the archive, to explore digitizing the collection with a commercial image scanner. Working with Jessica Mink, an archivist of the Harvard-Smithsonian Center for Astrophysics, Grindlay and Doane determined that a commercial scanner could produce suitable digital images but also found that such machines were too slow. Working full-time, it would have taken over 50 years to digitize the plates in the Harvard archive with commercial scanners.
Doane presented a talk about the problem at a meeting of the Amateur Telescope Makers of Boston whose clubhouse is located on the grounds of MIT's Haystack Observatory. Bob Simcoe, a club member and retired engineer, volunteered to help design a machine suitable for the task. The machine needed to position and record the stellar images on the plates to within half a micron and account for different emulsions, plate thicknesses and densities, exposure times, processing methods and so on. Software was developed by Mink, Edward Los, another volunteer from the club, and Silas Laycock, a researcher. Thanks to a grant from the National Science Foundation and donations of time and material, creation of the scanner began in 2004. The scanner was completed and tested in 2006. Over 500 plates were imaged before the project ran out of money in July 2007.
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