Astronomical interferometry, illustration. Interferometry is a technique where electromagnetic waves (red and blue) are superimposed. When used in astronomy, the observations of two separate telescopes can be compared and combined to produce a higher-resolution image of an astronomical object (here, a distant star). Examples are the Very Large Array and the Atacama Large Millimeter Array for radio telescopes, but the technique is used extensively for optical (visible light) telescopes as well.