The years 1877-1919 proved to be extraordinarily productive for Harvard College Observatory. Under the directorship of the entrepreneurial Edward Charles Pickering, the routine usage of astrophotographic observation was implemented. The photographic process could detect stars and other objects which the unaided human eye could not. Pickering's ambitious plan was to photograph the entire sky and to systematically catalogue each star visible in the resulting images. In order to accomplish this massive undertaking, Pickering hired a corps of women workers who came to be know as "computers" and whose overwhelmingly successful teamwork produced a copious amount of data.
Overseeing the work of the computers, renowned for her disciplined methods, was Williamina Paton Stevens Fleming who had formerly been Pickering's housekeeper. Fleming and her charges diligently inspected the images on the photographic plates and carefully calculated each star's visual magnitude. The brighter stars were also categorized by spectral type. Additionally, Fleming was responsible for preparing and editing the massive amounts of data produced by the computers for publication in the Annals of the Astronomical Observatory of Harvard College. Under her charge fell the production, from original observation to data compilation and on to final proofreading, of all other print materials issued by the Observatory. Remarkably, in her years as an observer, 1881-1911, Fleming herself classified a total of 10,351 stellar spectra, discovered more than 300 variable stars and 10 novae. She also first identified numerous other celestial objects which her keen eye detected on the photographic plates and which had previously been unnoticed in the heavens. In 1899 she was appointed Curator of Astronomical Photographs thereby becoming the first woman to be granted a formal appointment at Harvard. By 1911, the collection of photographic plates had grown to 200,000.
Volume XXIV of the Annals appeared in 1890 and contained information pertaining to position, magnitude and observational notations for 20,125 stars. Subsequently, in 1894, Seth Carlo Chandler, an associate of the Observatory who was a proponent of visual astronomical observation without the enhancement of photography, publicly impugned the work claiming to have found "incongruities" in the data pertaining to 15 stars which had been published in the volume. Pickering satisfactorily explained these aberrations and fully exonerated the Observatory's work and methods. On January 9, 1895, the New York Times declared: "Harvard's Accuracy is Asserted; Prof. Pickering Defends the Astronomical Catalogue Against Certain Charges and Inferences."
When reconsideration did determine that certain minor errors did exist within Volume XXIV of the Annals, an Errata appeared in Volume XXIII, Part II, which was later published in 1899. Appropriately, the very same hand which was so intrinsic to the gathering of the data therein and even directly responsible for its production, that of Williamina Fleming, applied the written corrections to the physical copy of Volume XXIV of the Annals which existed within the Observatory Library and which is still available in the John G. Wolbach Library.
Photographs courtesy of the Harvard College Observatory.