Radio astronomy uses radio waves to study regions of space. Single-dish radio telescopes produce blurry images. Interferometry is a technique used to overcome the blurring and produce sharper radio images. The spacing between the radio telescope dishes in an interferometer determines the size of the objects that can be resolved by the interferometer. Using many dishes together in an interferometer array allows astronomers to form more complete images of objects.
Most sources have a complicated shape, with both large and small-scale structure.
Better images of observed sources can be formed if more than two dishes are used at once, and as more powerful computers have become available signals from more dishes have been able to be combined electronically. The computer must carefully coordinate the movements of all the dishes. Each dish can be combined as a pair with every other dish to maximise the number of spacings between dishes. This maximises the size-scales in the source about which the interferometer can obtain information. The rotation of the Earth under the source then changes the distances from the source to each dish.