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Sunset Eclipse of X-Rays and Visible Straylight

Image name: High_Time_Res_Sunset.png (click image to enlarge)
Image size: 7.82400 KB (640x512)
Date submitted: 22-Dec-1994


   This figure demonstrates the time difference between x-ray and
visible straylight sunset eclipse for SXT.  The data were taken in flare
mode on 19-Dec-1994.

   The diamonds are the straylight eclipse observed with an SLS-type
exposure: DPE=2, NB filter, shutter closed.  The other curves are for
the x-ray signal in a 64x64 HR PFI.  They have all been normalized to
the same starting intensity but not otherwise fudged.  The + curve is
for a west limb source and the triangles are for a strong source near
the east limb.  The stars are for a very faint part of the corona above
the east limb.  The second hump in this curve is the actual straylight
in this image as the PFI was taken where the AlMg straylight is

   Although these curves indicate that the interval 10-30 seconds before
FEM sunset is a safe interval I have often seen SFT images taken at
times between 25 and 30 sec that were contaminated by east limg x-ray
sources.  Allowing for a 5 sec exposure says that we should be able to
work with a 15-25 sec before sunset window.

                                         L. Acton  12/22/94

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