The errors associated with a segmented primary mirror limit the image quality obtainable with those astronomical telescopes which employ them. It is necessary to derive the effects of segmentation errors on image quality in order to determine realistic error budgets for such telescopes. The main segmentation errors are misalignment and piston of

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At sufficiently low frequencies, no ground-based radio array will be able to produce high resolution images while looking through the ionosphere. A space-based array will be needed to explore the objects and processes which dominate the sky at the lowest radio frequencies. An imaging radio interferometer based on a large number of small

We have analyzed the differences in the oscillation eigenfrequencies measured over more than two years of GONG observations (December 1995-April 1998) and SOI/MDI observations (May 1996-July 1998). We have inverted these data to look for signatures of the solar activity cycle on the stratification. A one-dimensional (radial) structure inversion

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This paper is the second in a series that models photospheric magnetic structures in terms of atmospheres having optically thin fluctuations of magnetic field and thermodynamic state (the MISMA hypothesis). We apply an inversion procedure to the polarization of Fe I λ6301.5 and Fe I λ6302.5 observed in network and internetwork regions with the