Draper, Henry (1837–1882)
The son of John William Draper, Henry trained to be a medical doctor but, because he completed all of his medical courses at New York University by the age of 20, he traveled in Europe for a year until he was old enough to graduate. In Ireland he visited, and was greatly influenced by, the Third Earl of Rosse, William Parson. Subsequently, he wove his interests in telescope-making and photography, developed during his travels, into his professional career. When he returned from Europe, Draper began preparing his own glass mirror, which he installed in his new observatory on his father's estate at Hastings on Hudson, New York. He started his astronomical research career by making preliminary studies of the spectra of the more common elements and photographing the solar spectrum. By 1873 he had produced a spectrograph that was similar to the visual spectroscope of William Huggins; he clarified the spectral lines by using a slit and incorporating a reference spectra so that elements could be identified more easily. The spectroscopic studies of Huggins and Norman Lockyer in Europe stimulated Draper's research and during the last years of his life he worked toward acquiring high quality spectra of celestial objects. After his untimely death, from pleurisy, his widow established a fund to further support a spectral studies program. In 1886 a team at Harvard College Observatory began the program to establish a useful classification scheme for stars and a catalogue of spectra. The Harvard project, named the Henry Draper Catalogue, completed in 1897, resulted in the first comprehensive classification of stars according to their spectra.
Herschel was a pioneer in celestial photography, and as a chemist contributed to the development of sensitized photographic paper (independently of Henry Talbot). In 1819, he discovered that sodium thiosulphate dissolved silver salts, as used in developing photographs. He introduced the terms positive image and negative image. Being diverse in his research, he also studied physical and geometrical optics, birefringence of crystals, spectrum analysis, and the interference of light and sound waves. To compare the brightness of stars, he invented the astrometer.
Related category• ASTRONOMERS AND ASTROPHYSICISTS
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