View of the 'Oxford heliometer' displayed at the Science Museum shown from the east side. This is a 7 inch refracting telescope with split-lens micrometer on a German equatorial mounting. It was built for the Radcliffe Observatory, Oxford by the company of A & G Repsold of Hamburg with optics by G Merz & Sons of Munich and was completed in 1849. The instrument was used to measure the parallax (a minute angular measurement) of nearby stars which is an indicator of their distance.
© Science Museum / Science & Society Picture Library