Mural Quadrant

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Mural quadrant made by Jeremiah Sisson
Manufacturer	Jeremiah Sisson
Production years	1770

Mural quadrants were used to measure the altitudes of astronomical objects. This particular 8-ft. brass quadrant was made by Jeremiah Sisson in 1770 for the private observatory of George III at Kew. It is very similar to those made by his father, Jonathan Sisson, who was the chief craftsman of George Graham, maker of the famous mural quadrant erected at Greenwich Observatory in 1725. The quadrants and other astronomical instruments made by the Sissons were highly prized and were installed by several foreign observatories.

[edit] How it works

The total range of the arc is 142 degrees, enabling observer to make measurements through the attached telescope from 90 degrees on one side of the zenith to 52 degrees on the other side.

[edit] In the Science Museum's Records

Inv. no: 1889-39