Jesse Ramsden FRS FRSE was a British mathematician, astronomical and scientific instrument maker. His reputation was built on the engraving and design of dividing engines which allowed high accuracy measurements of angles and lengths in instruments. He produced instruments for astronomy that were especially well known for maritime use where they were needed for the measurement of latitudes and for his surveying instruments which were widely used for cartography and land survey both across the British Empire and outside. An achromatic eyepiece that he invented for telescopes and microscopes continues to be known as the Ramsden eyepiece.
Mezzotint by J. Jones, 1790, after Robert Home. This, the only portrait of Ramsden shows him with the dividing engine in front of him and a great circle made for the Palermo Astronomical Observatory behind him. Ramsden never wore fur coats but the artist added it because the painting commemorated an order from the Empress of Russia that Ramsden had worked on.
The 5-foot diameter Palermo circle manufactured by Jesse Ramsden to measure apparent positions of astronomical objects.
A brass refractor telescope by Jesse Ramsden at the Herschel Museum of Astronomy
A dividing engine is a device employed to mark graduations on measuring instruments.
Dividing engine at the Michigan Museum of Surveying
Dividing engine at the Museo Galileo in Florence.
Circular Dividing Engine
