Imaging performance and tests of soft x-ray telescopes

Photos obtained during 5 min. of observation time from the flight of our 10 inch normal incidence soft x-ray (λ = 63.5 angstrom) telescope on September 11, 1989 are analyzed and the data are compared to the results expected from tests of the mirror surfaces. These tests cover a range of spatial periods from 25 cm to 1 angstrom. The photos demonstrate a reduction in the scattering of the multilayer mirror compared to a single surface for scattering angles above 1 arcmin, corresponding to surface irregularities with spatial periods below 10 μm. Our results are used to predict the possible performance of future flights. Sounding rocket observations might be able to reach a resolution around 0.1 arcsec. Higher resolutions will require flights of longer durations and improvements in mirror testing for the largest spatial periods.