Cambridge Optical Aperture Synthesis Telescope

COAST was the first long-baseline interferometer to obtain high-resolution images of the surfaces of stars other than Sun (although the surfaces of other stars had previously been imaged at lower resolution using aperture masking interferometry on the William Herschel Telescope).

The COAST array was conceived by John E. Baldwin and is operated by the Cavendish Astrophysics Group. It is situated at the Mullard Radio Astronomy Observatory in Cambridgeshire, England.