Almucantar instrument at the University of Durham, England. This almucantar was built by the British astronomer Ralph A. Sampson (1866-1939) and described by him in a journal article in 1900. This was one of several such devices being built, all improving on the initial almucantar design by S. C. Chandler in 1879. An almucantar is designed to be used like a transit circle, to determine the position of stars and other astronomical objects, but is designed to be steadier and easier to use, leading to improved results. The design involved a steady base containing mercury, and a telescope on top floating in the mercury. This allows for more stable observations and improved accuracy in readings.