Robert Trumpler 1886-1955 photographed nearly all the bright open clusters about 50 in number with the slit less quartz spectrograph attached to the Crossley Telescope with exposures of from 5 to 7 hours. This was done during 1925-1926. This work would be used in the Trumpler Catalogue of clusters which was published in 1930. This catalogue is still used today by astronomers.
The Crossley Telescope was owned by Edward Crossley in Halifax, Yorkshire from 1885 until 1896, however the skies above Halifax meant that the telescope could not be used to best effect. In 1896 it was donated to the Lick Observatory in California where it would be used in many pioneering projects early in the 20th century.
The slit less spectrograph was designed and constructed by C Donald Shane 1895-1983 while he was assistant professor of maths and astronomy at the university of California for the purpose of applying it to the study of nebulae.