About the Project
The Harvard College Observatory spent more than a century photographing the night sky. More than 500,000 glass plate photographs remain from this field-altering investment in science and technology. Today, these plates are being digitized with the purpose of making the analog data available to scientists and the public with the purpose of studying phenomena otherwise hidden by the depths of time. While most plates contain 50,000 to 100,000 stars, very few on each plate have ever been examined or studied. DASCH, a Digital Access to a Sky Century at Harvard, aims to preserve the plates by digitizing them while also measuring both the position and brightness of any object on the photograph. As part of the process we have to digitize the metadata associated with each image. This is of the utmost importance for without the metadata we cannot correctly understand how the brightness and position of stars change with time. With less than 25 years of continuous observations of the sky with CCD cameras, the photographic glass plate collection allows us an unique way to interpret the variations of stars over more than a century.
As the metadata has been transcribed and the plates digitized, scientists have already found unexpected phenomena. One of the most exciting finds are black hole-dwarf star pairs that erupt for a month every 50-100 years. Before DASCH only two of these were know to exist. In the past two years, with less than 10% of the plates having been digitized, DASCH has found three more. The hope is that as we find more of these and characterize them, we can better understand the evolution of stars in our galaxy. Another exciting result was the identification of stars whose brightness changes by a factor of 4 on times scales of 50-100 years. Regardless of which telescopes you used today, the biggest ones on the ground like Keck in Hawaii or the Hubble Space telescope, without the possibility of evaluating the stars over long time periods these discoveries would be impossible.
We invite both you, the public, and scientists from around the world to check out our website http://dasch.rc.fas.harvard.edu/. If you navigate to the search image tab you can type in any object you want. If we have digitized plates for which that object is included, the website will generate a plot of its brightness vs. time. We hope you can help us transcribe the metadata so that we can digitize the plates and make many more exciting discoveries.
The AI #45 logbook contains information about photographic plates AI23787-AI24155, which were taken between December, 1924 and July, 1925 with the Voigtlander 56600 telescope lens in Cambridge, Massachusetts.
For more information about the DASCH project, please visit our website at http://dasch.rc.fas.harvard.edu/.
Before iPhones, laptops, and even punch-card computers there were human computers, some of whom worked at the Harvard College Observatory. Most recently seen on the TV series COSMOS with Neil Tyson, these women made some of the most important discoveries in astronomy in the early 20th century. Please come help us transcribe the logbooks so we can preserve and digitize this very valuable resource.