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T. Nordgren (Lowell Observatry)
In four years of operation the Navy Prototype Optical Interferometer (NPOI) has regularly observed stars brighter than V = 5.0 in the angular diameter range of 1.5 to 8.8 mas. The majority of these stars are late-type giants and supergiants which include four of the brightest Cepheid variables in the northern sky. The repeated observation of large samples of nonvariable stars has lead to confidence in the accuracy and precision of NPOI diameters. Such confidence opens the way for a variety of interesting astrophysics including comparisons of NPOI diameters with those from interferometers at other wavelengths. One result is the confirmation of the overtone pulsation of Polaris deduced from the non-agreement of the observed radius and that predicted by theoretical and empirical period-radius relations for fundamental mode Cepheids.