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Vignette & Scatter Correction Comparison

Image name: Vignette_and_Scatter_Test.png (click image to enlarge)
Image size: 6.52800 KB (512x512)
Date submitted: 30-Oct-1996

							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.

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