Astronomical Photographic Plate Collection – Harvard College Observatory Plate Stacks
Now available online, Astronomical Photographic Plate Collection in Harvard College Observatory Plate Stacks is an archive made up of over 500 000 images, of the night sky from both the northern and southern hemispheres. They are all in the process of being digitized by the DASCH (Digital Access to a Sky Century @ Harvard) program, which began in 2009. As of September 2017, 200 000 plates have been scanned.
This archive came about at an interesting time in American history, as the Harvard College Observatory, where the majority of these plates were made, was founded in 1839, just a few years after the Hailey’s Comet craze. This even sparked the public’s interest in astronomy, and interest in observatories. This I also the year the Daguerreotype was invented, and photography was beginning to become perfected. In 1940, John Draper, the Director of the Observatory made the first daguerreotype of the moon, and continued to experiment with the process of making photographs through the telescope. Before then, all images of the night sky were drawn by hand, from human observation. Now the technology was available to make more accurate images, and at a much faster pace. From this point on, the standard is to use photographs for res
earch. The plates were made until 1992, which a brief gap in 1950.
The plates were still analysed by humans, which lead to the group of women being hired as computers in 1975. Responsible for cataloguing and analysing the images made overnight, many of these female computers went on to careers in Astronomy, and are responsible for many important discoveries. Willamina Fleming was initially hired as the house keeper for the observatory, but quickly rose to computer, and then Curator of Astronomical Images. Female computer, Cecelia Payne earned the first PhD in astronomy from Harvard for her work analysing the composition of the sun’s atmosphere, and Henrietta Leavitt’s work cataloguing the brightness of stars was used by Hubble to defend his theory that the universe is expanding.
Through the digitization of these plates, the information is being conserved. You can see how fragile the glass plates are as objects, but the imperfections are included, and not erased with photoshop, as they are a project of the process. These plates would have been expensive at the time, so even less successful images, and ones were bugs have gotten in the way, are all kept as there is still some useful information on the plate. The imperfections are something that would not be included in collections today, as contemporary astrophotography’s aim is to have no errors, or indication of the human hand.
Along with the glass plates, the sleeves they are stored in are being catalogued, and the log books are being digitized. This work is being conducted by the Current Curator of Astronomical Images at the Observatory, Smith Zrull, in attempts to identify all of the female computers who worked on this decade long project. Of the 130 suspected, 40 are still not identified, but should be credited for their contributions. Much of this work is being done by primarily volunteers through the Smithsonian Institute.
Primarily funded by the National Science Foundation, the plate collection is currently being used in the study of Time Domain Astronomy/Astrophysics. It allows for a unique study of how stars have changed over a hundred years. It also provides a parallel look at how the role of women in astronomy have changed over the last 100 years. While the digitization project will never be able to capture the same tactile quality of the primary sources, it does open up possibilities for anyone to access this information regardless of ability to travel/finances/education. The site is clearly designed for scientific research, but with a bit of time, anyone can work with the search parameters to pull up images that we all wonder about, and want to understand – the cosmos.