Coherence theory of a radio telescope

A new theory is developed to describe the operation of a radio telescope consisting of an array of two-element interferometers. The theory is based on recent developments in the theory of partial coherence, which employs an expansion of the scalar field amplitude into an angular spectrum of plane waves. Expressions are found describing the correlation of the field amplitudes in the antenna plane which are more general than usually obtained, and which suggest a simplified data processing procedure which might yield improved images. The usual quasi-monochromatic approximation is made and the conditions under which it is valid are discussed in detail. Finally the theory is connected with the usual procedure for producing images of the radio sources and the existence of an obliquity factor is shown which could affect images over a large field of view.