on Earth, and, in Carrington coordinates, the longitude is fixed for the Sun's rotation.

Stonyhurst system

The Stonyhurst heliographic coordinate system, developed at Stonyhurst College in the 1800s, has its origin (where longitude and latitude are both 0°) at the point where the solar equator intersects the central solar meridian as seen from Earth. Longitude in this system is therefore fixed for observers on Earth.

Carrington system

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