One of two heliographic coordinate systems used for identifying the position of features on the Sun’s surface. In the Stonyhurst system the zero point is set at the intersection of the Sun’s equator and central meridian as seen from the Earth. Longitude increases towards the Sun’s western limb. A solar feature will have a fixed latitude as it rotates across the solar disk, but its longitude will increase. This is in contrast to the Carrington heliographic coordinate system, where the longitude remains approximately fixed in time. Stonyhurst coordinates are named after Stonyhurst College in Lancashire, England, where they were devised in the nineteenth century.