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Date submitted: 30-Oct-1996
30-Oct-96 L. Acton Vignette & Scatter Correction Comparison The figure compares the effect of applying an x-ray scatter correction before or after vignette correction. The data are from the following offpoint image where the heavy horizontal bar indicates the position of the sun and the vertical dashed line is sun center. 26-AUG-92 22:30:36 QT/H Open /Al.1 Half Norm C 32 60418.0 512x512 The upper (+) curve is made from a sum over the image in the y-direction of a composite image which was vignette-corrected before the scattering image was computed with SXT_SCATTER and subtracted. The lower curve is for the case where the scatter was computed from the composite image without vignette correction and then the scatter-corrected image was corrected for vignetting with SXT_OFF_AXIS. Neither procedure is perfect but the procedure with scatter correction appears to be preferred as we expect no real coronal signal at the LH side of this image. What the result of this experiment indicates is that, to first order, the x-ray scatter off of the SXT mirror is vignetted in the same manner as the focussed signal.