Here's the caption:

A print of this HCO photograph was found in an album that had once belonged to Annie Jump Cannon.The print was dated by tracing the HCO serial number on it to the record books in the Harvard College Observatory Collection of Astronomical Photographs. The women were identified by comparing the print to other HCO photographs on which Margaret Harwood or Annie Jump Cannon had noted the names.

This picture which includes Edward Charles Pickering, the Director of HCO(1877-1919), was taken on 13 May 1913 in front of Building C, which faces north. At that time it was the newest and largest building of Harvard College Observatory. It was specially built of brick to protect the astronomical data and glass negatives from fire. Since the astronomical photographs were stored on the ground floor and most of the women worked on the top floor, the building had a dumb waiter to convey the plates up and down. The women all worked in a large room on the east end of the third floor. Pickering had his offices on the west end across the central hallway. All the other men worked on the lower levels.
At the far left of the photograph is Margaret Harwood (AB Radcliffe1907, MA University of California 1916), who had just completed her first year as Astronomical Fellow at the Maria Mitchell Observatory. She was later appointed director there, the first woman to be appointed director of an independent observatory. Beside her in the back row is Mollie O'Reilly, a computer from 1906 to 1918. Next to Pickering is Edith Gill, a computer since 1989. Then comes Annie Jump Cannon (BA Wellesley 1884), who at that time was about halfway through classifying stellar spectra for the HenryDraper Catalogue. Behind Miss Cannon is Evelyn Leland, a computer from 1889 to 1925. Next is Florence Cushman, a computer since 1888. Behind Miss Cushman is Marion Whyte, who worked for Miss Cannon as arecorder from 1911 to 1913. At the far right of this row is Grace Brooks, a computer from 1906 to 1920.
Ahead of Miss Harwood in the front row is Arville Walker (AB Radcliffe 1906), who served as assistant from 1906 until 1922. From 1922 until 1957 she held the position of secretary to Harlow Shapley, who succeeded Pickering as Director. The next woman may be Johanna Mackie, an assistant from 1903 to 1920. She received a gold medal from the American Association of Variable Star Observers (AAVSO) for discovering the first nova in the constellation of Lyra. In front of Pickering is Alta Carpenter, a computer from 1906 to 1920. Next is Mabel Gill, a computer since 1892. And finally, Ida Woods (BA Wellesley 1893), who joined the corps of women computers just after graduation. In 1920 she received the first AAVSO nova medal; by 1927, she had seven bars on it for her discoveries of novae on photographs of the Milky Way.
Barbara L. Welther published the photograph and some of the text in a note about 'Pickering's Harem' in Isis 73, 94 for March 1982.