The scattering wings of the SXT PSF begin to dominate the narrow core at about 20 arcsec
from the center-at a level about 5 or 6 orders of magnitude down from the peak (see Fig. 4 in
the Tsuneta, et al. (1991 `Red Book'). The
scattering wings may be characterized from over-exposed flares observed in
FFI mode such as 6-Sep-92 18:48. Hara (to be published) has derived the
following expression which describes the shape of the PSF wing for a flare
of 
K, through the thin filters
per full resolution SXT pixel and per unit intensity in the flare, with r
specified in arcsec. The scattering
properties of the mirror are wavelength dependent. This introduces a
dependence upon input spectrum in correcting for the PSF scattering wings
in data analysis. Hara represents this dependence in terms of a ratio of
the mean wavelength of the flare and the mean wavelength of the reference
( K) spectrum and gives the following expression for the PSF wing for
other source temperatures.
where 
is the average wavelength recorded by SXT through either the
Al.1 or AlMg filters at temperature 
.
Scattering wing corrections have not yet been derived for the thicker filters and programs for use of the preliminary algorithms derived by Hara have not yet been released for general use because of concerns of their applicability away from sun center.