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Imaging properties of Wolter I type x-ray telescopes.

By ray-tracing methods we have investigated various configurations of Wolter I type x-ray telescopes. For the criterion of image quality the shape of the line spread function has been chosen. The angular resolution we find herewith in a large region of the basic parameters appears to be more than three times higher than results from the rms blur circle criterion. We have concluded that in most cases of practical interest the paraboloid-hyperboloid combination has to be preferred to the Schwarzschild system. In all cases it is possible to find a solution giving an extra improvement of the angular resolution with a factor between,2 and 4 when we describe the mirror shapes with polynomials.