Navy Prototype Optical Interferometer

Since the invention of the telescope, astronomers have been striving for clearer definition of the objects they observe; this has led to the development of larger and larger telescopes. As we increase the size of a telescope, faint objects become easier to see and the detail seen in the object improves as well. The physical effect that limits the resolution of a telescope is called diffraction with the amount of diffraction decreasing with increasing telescope size and vice versa. To illustrate this behavior let's consider a pair of stars lying close together on the sky. One such pair could be the binary star system Mizar, visible to the naked eye and found in the handle of the Big Dipper. In the figures to the right, we have shown the hierarchy of stars in the Big Dipper to aid the reader in understanding the Mizar system. Mizar lies very close to Alcor, another naked eye star, and both may be seen as distinct stars by the unaided eye. This visual pair of stars is not physically connected by gravity. Mizar itself is a pair of stars, Mizar A and Mizar B, that are separated by about 14 seconds of arc, too close to be seen by the naked eye as a distinct pair. The eye, which has a resolution of about 2 minutes of arc, discerns the Mizar star system as a single star. However, with modest optical aids (binoculars, for example) it is resolved into a close pair. <br.< br>