An interferometric technique based on a white light fringe setting was used to set mirrors defining a base plane in a Michelson stellar interferometer to coplanarity. The method is in principle capable of extension to very large separations, and the precision of visual setting is of the order of the wavelength of light.
© 1980 Optical Society of America
R. Q. Twiss and W. T. Welford, "Adjusting spatially separated plane mirrors to coplanarity," Appl. Opt. 19, 2416-2418 (1980)