Since its founding in 1891, many people have passed through the doors of the Vatican Observatory. A quick perusal of our guestbook reveals several Names, including Popes, nobel laureates, astronauts, actors, and saints. Today’s guestbook entry is from November 29, 1913, when John Parkhurst made a visit.
Next to his name, John Adelbert Parkhurst FRAS (1861-1925) wrote, “Yerkes Observatory, Williams Bay Wis. U.S.A.” He was an astronomer who had been at Yerkes Observatory since 1898.
Parkhurst’s astronomical specialty was stellar photometry. Bear in mind that this was an era before C.C.D.’s or even photomultiplier tubes–you had to determine brightness based on the image of a star on a photographic plate.
He published more than 100 papers over his career.
In 1912, he published the “Yerkes Actinometry” in the Astrophysical Journal. This was a catalog of the magnitudes, color indices, and spectral classification of every star brighter than magnitude 7.5 between declination 73 degrees and the celestial north pole. [Author’s note: the paper itself is a fascinating read if you are interested in how photometry was done in the era of photographic plates. Plus, it has pictures of the instruments used.]
There is a crater on the Moon that bears his name.