Our Collection
The Harvard Plate Stacks collection stretches back to the dawn of photography to the present. At the core of our collection are the nearly 600,000 glass plate negatives of the night sky. This represents the largest collection of its type in the world, where nearly one out of four of these astronomical plates resides within our collection. This collection was founded through the support and endowment left by Anna Palmer Draper in honor of her late husband, Henry Draper. Central to our history is the individual and pioneering legacies of over 200 Women Astronomical Computers whose discoveries help shape the way we see the universe today.
The astronomical size of the collection means much of our holdings has yet to be inventoried or catalogued. However, our database StarGlass is over 1.2 petabytes of our collection, digitized and made accessible. This represents two of our major collections, 60% of our glass plates and their jackets, and over 2,500 scientific notebooks made by those who worked within our collection, known as Project PHaEDRA. This is the easiest way to gain access to specific materials and is even available for you to search in a customized way through open API access.
While StarGlass provides a universe of discovery, there are key parts of our collection yet to be included in it. Almost all of our direct image plates are either fully digitized or have a metadata record in StarGlass, nearly 200,000 glass plates of individual spectra and spectral field plates are not included. Also, large holdings from the HCO and SAO Meteor departments have not yet been included in the database.
Finally, our collection includes the very earliest examples of astrophotography and analogue photographic materials. These include daguerreotypes, Apollo lunar photography, sunspot plates, and 150 years of eclipse photographs. Our collection also holds significant archival materials and ephemera.
Finally, our collection continues to grow. Over the decades, different departments at the Center for Astrophysics have deposited their analogue materials in our holdings. Relatively small but equally important photographic materials, including thousands of spectra and plates, have also been given to the Plate Stacks by outside organizations and individuals. The curators of the collection have also actively acquired materials related to our holdings and history. You can read more about the kinds of materials we have added to and are looking to add to our collection by reading our collection development policy.
Contact us to ask for help in finding materials or to inquire if we have items in our collection.
This represents the largest part of the collection.
This collection comprises over 2,000 bound ledgers that record the metadata for each photographic plate. They are also divided into plate series, just like the glass plate negatives. By convention, each night of observations for an instrument would be recorded, and the observer would record the information for the exposure of each plate as it was made.
The Observatory used preprinted tables for most of the duration of the project. In the standard table, columns were printed titled: "No. [Plate Number]", "Class", "Object [Or Subject of the Plate]", "R.A. [Right Ascension]", "Dec. [Declination]", "Obs. H.A. [Observatory Hour Angle]", "Obs. Dec. [Observatory Declination]", "Tel. E. or W. [Telescope East or West]", "Load", "Focus", Prisms", "Sky at Start", "Stopped", "Exp. [Exposure Duration]", "Cl'ds [Clouds]", "Cl'k [Clock]", "Dew", "Ref. [Reference]", "Obs'r [Observers]", "REMARKS". Right Ascension and Observatory Hour Angle are formatted in hours and minutes (hh:mm). Declination and Observatory Declination are recorded in positive or negative decimalized degrees (+86.25). Observers, or, more specifically, the telescope operator and thus the photographer, are most often recorded only by initials.
Although not every logbook or every observer recorded all of these factors, the logbooks are the primary source of all metadata for the photographic plates. Logbooks are also where observers and astronomy staff would record any changes, maintenance, or improvements made to the telescope or instrument. These records were considered so vital that the bound copies of the logbooks were to be kept with the instrument, and the records were regularly copied onto loose-leaf pages. It would be these loose-leaf copies that would be shipped with the glass plate negatives when they were sent from remote observatories to the Plate Stacks. The information would be transcribed from these loose-leaf copies that the information would be transcribed onto the plate jackets. Thus, the bound logbooks are considered a source of "truth" when reconciling discrepancies between plates and their jackets. Logbooks contain written discussions between computers and observers when information did not match. The logbooks document the many different redundancies built into the working procedures.
The DASCH Project created rudimentary images of the logbooks, and only a segment of the metadata was transcribed into the database. The imagery and scans of the logbooks are not readily accessible online. A small portion of logbooks that were transcribed later in the project is available on the Smithsonian Transcription Center. They are under completed projects and begin with the title "Harvard-Smithsonian Center for Astrophysics DASCH project- Logbook". DASCH did not directly transcribe the logbooks. Rather, volunteers transposed the data into a standard format related to each plate, and skipped over other metadata. DASCH and now StarGlass only record: Logbook Page, Plate Number, Class, Right Ascension, Declination, Start-time, Observatory Hour Angle, Observatory Declination, Stop-time, exposure duration, date, and remarks. Most notably, DASCH and StarGlass do not have the astronomical subject or the observer recorded in their metadata because of this omission.
StarGlass: Images of the logbooks and their pages are not available through StarGlass. The transcribed metadata is searchable in StarGlass, though if a plate was scanned with the DASCH Scanner, the "Exposures" tab shows modern calculated R.A. and Dec. derived from digitally fitting the image.
This collection of mostly bound notebooks numbers over 2,500 objects. Project PHaEDRA is an ongoing transcription project that makes these important historical and scientific materials accessible to researchers and the public. This transcription project and the materials it focuses on have become synonymous. The acronym stands for "Preserving Harvard's Early Data and Research in Astronomy," and while the collection includes notebooks from the prephotographic era of the Harvard College Observatory, the lion's share of the materials date to the era of astronomical glass plates and particularly the Women Astronomical Computers. The majority of these notebooks are the different calculations, processing, and work done with the glass plate collection.
These notebooks are either segmented by individual astronomers and their own projects, or by a specific type of work, such as "Objects looked up for outsiders by request", "RH Plates PTM" or "Meridian Photometer Remarks". It is important to note that many of the authors of this collection are men, but it is the largest manuscript and archival collection of the Women Astronomical Computers at Harvard. The scope of this collection is not rigid and has changed over time; it roughly reflects what was preserved and kept together.
Originally, the notebooks in this collection were kept on the top floor of the Plate Stacks' current location, in an area with the card catalog for the plates as well as where the plate examination equipment was located. These notebooks were considered a vital reference regarding the plates, and thus they were considered part of the collection. Plate annotations, plate jackets, and other notebooks reference these notebooks and specific pages. As an example, the jacket for plate AC02155, has a note written by Henrietta Swan Leavitt, "Superposed on D12559 (=AC5491) See H.S.L. Book XXII, 31," which points future researchers to page 31 of Leavitt's notebook number 22. The current identifier is now Phaedra0947, but using the author "Leavitt" and the sequence number "22", the item can still be found.
As early as the 1940s, parts of this collection were stored on the restricted shelves of Widener Library. This locked "caged" section allocated for the Observatory was labeled KG, and thus items in the collection began to get a "KG Call number." There are two "deposits within the KG scheme denoted as KG11365 and KG11366, with the decimal number documenting the order in which they were placed (e.g., KG11366.125 was next to KG11366.126 in the Widner). The KG number is rarely, if ever, referenced outside of cataloging and administrative records. However, they are still documented as they denote a historic, though not original, order to the materials. The materials at Widener were later stored at the New England Books Depository, and the entirety of the collection would be stored at the Harvard Depository facility. It was during this era that the collection's tracking and existence of the collection were obscured by subsequent curators until 2017, when the then-curator, Lindsay Smith Zrull, rediscovered it. She would then transfer the stewardship to the Wolbach library, where they would receive their Phaedra number, which follows the order of previous schemes while continuing to number much of the collection that was never stored at Widner.
StarGlass: The entire collection has been digitized and is accessible on SciX/ADS. The catalog records of all of the volumes, as well as the full text of those that have been transcribed, can be searched through ADS/SciX. Though using our main Finding List webpage or the Finding Aid can be easier and more intuitive to browse. Individual pages of the PHaEDRA notebooks are linked to plates in the "Mentions" tab in StarGlass. These linkages were made possible through the Zooniverse Project, "Star Notes," completed during 2020-2023, though they will not be exhaustive, it provides another layer of connection across materials and mediums.
