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Date submitted: 19-Dec-1994
PROCESSED SFC STRAYLIGHT-CORRECTION IMAGES This figure illustrates the straylight pattern for each of the SXT analysis filters. These HR images have all been rebinned to 256x256 for display here. They were all taken between 17 and 21 seconds before FEM sunset and all are DPE=25 (5 sec) exposures. Location and size of the sun is indicated by the circles. The smoothing produced by the lataest version of SFC_PREP is quite good for HR images through all filters. It has not been tested on QR or ND filter images as yet. Two examples are given for Al.1 to demonstrate the effects of pointingfor this filter. These two images (A and C) are displayed with SFD_COMP scaling. All of the others are scaled linearly. Image B is a difference image of SFC A and the corresponding dark_subtracted SFT image, clipped to +/- 4 DN to show some of the fine scale structure of the straylight image. Image E is a corresponding difference image for Mg3 -- image D. It was a bit of a surprise that Mg3 shows so much interesting structure. Panel J illustrates the strength of the straylight signal for each of the filters. The righmost Al.1 datum (#6) corresponds to east offpointed image C. It is clear why we use AlMg for our dark exposures and a bit surprising that the straylight for Be is so bad. I am now confident with the quality of the smoothed SFT images. Since these are prepared from DARK_SUB corrected images they will be improved further in accuracy when the orbit-corrected dark subtraction is available. The streak in the upper right of image A is an example of spurious over-correction by bad dark frames in the present SDC data base. Once we fully understand the criteria for time to sunset selection we should be able to fully automate the preparation of SFC correction images. The problem of better correction for the Al.1 "network" fine structure must still be addressed. L. Acton 12/19/94