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"American Method in Astronomical Observation"
From the collection of National Museum of American History. Free to download, adapt and use — no permission needed.
About this work
From its infancy, timekeeping has depended on astronomy. The motion of celestial bodies relative to the rotating Earth provided the most precise measure of time until the mid-twentieth century, when quartz and atomic clocks proved more constant. Until that time, mechanical observatory clocks were set and continuously corrected to agree with astronomical observations.
National Museum of American History’s own descriptionCredit line"American Method in Astronomical Observation". ca 1850. William Bond & Son. National Museum of American History. CC0.
