"Back of the Envelope"

An informal illustration of technology in action


Sketch by Jonathan Sills
The Zenith Sector

The zenith sector pointed straight and directly overhead. A telescope rotated on a pivot and allowed astronomers to measure the zenith distances (the angle between the star and the highest point in the sky) of celestial bodies. This also necessitated aligning the instrument in the meridian (a line through the poles).

Since the graduated scale was so low to the ground, the astronomer usually had to lie on his back or a special reclined seat in order to effectively make observations with the zenith sector.


VIEW A ZENITH SECTOR FROM THE MUSEUM'S COLLECTION

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