Object notes Associations
"Broken" transit instrument, made in New York by Stackpole & Brother. Transferred from the U.S. Naval Observatory.
This is one of eight identical instruments built for the United States' expeditions to observe the 1874 Transit of Venus. The objective lens has 6.5 cm clear aperture. This type of instrument was used, with a chronometer, to observe "transit times", i.e. to note the exact time that a star crosses the observer's meridian. The term "broken" transit comes from the use of a mirror (or, in this case, a prism) to change the path of incoming light - to "break" the light path and direct it to a stationary observer's position. This instrument is identical to catalog #327,720, another Stackpole "broken" transit in the Smithsonian collections.
Catalog #327,719 Physical Sciences Collection, Smithsonian Institution
Object contributed by National Museum of American History, Smithsonian Institution