The first images from an optical aperture synthesis array: mapping of Capella with COAST at two epochs.

We present the first aperture synthesis maps obtained using closure phase techniques with a separated-element optical interferometer. Maps of the double-lined spectroscopic binary Capella (alpha Aurigae) were obtained at 830 nm with three elements of the Cambridge Optical Aperture Synthesis Telescope (COAST) in September 1995. These maps show clearly the milliarcsecond orbital motion of the system over a 15 day interval. The image quality is comparable to that of VLBI images obtained using similarly sparse radio synthesis arrays, and the location and motion of the binary components are in excellent agreement with the predictions of the latest set of orbital elements. These data demonstrate for the first time the feasibility of operating long-baseline optical/near-infrared interferometers for high-dynamic range high-resolution imaging.