Put a satellite in a circular orbit about 42,000 kilometres from the center of the Earth (36,000 kilometres or so above the surface) and it will orbit once in 24 hours. Because that matches Earth’s rotation period, it is known as a geosynchronous orbit. If that orbit is also in the plane of the equator, the satellite will hang in the sky over a fixed location in a geostationary orbit.

As predicted in the 1940s by futurist Arthur C. Clarke, geostationary orbits are in common use for communication and weather satellites, a scenario now well-known to astroimagers.