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Finding out ORGX ORGY: Difference between revisions
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The error you make in the determination of ORGX ORGY should in principle be less than half of the distance between two spots. If you have a reasonable estimate (from one of the methods above), but the error is bigger than that, ''you can still find out the true ORGY ORGY by inspecting [[IDXREF.LP]] . This works best if [[COLSPOT]] has seen a significant fraction of all frames.'' | The error you make in the determination of ORGX ORGY should in principle be less than half of the distance between two spots. If you have a reasonable estimate (from one of the methods above), but the error is bigger than that, ''you can still find out the true ORGY ORGY by inspecting [[IDXREF.LP]] . This works best if [[COLSPOT]] has seen a significant fraction of all frames.'' | ||
== The case of a swung-out detector == | |||
In the case of a swung-out detector, there is a large discrepancy between the direct beam position and (ORGX,ORGY). E.g. assuming the detector is swung out by 2theta in the horizontal, then ORGX has to be adjusted w.r.t. the value obtained in steps 1-5 (above), by an amount given by basic geometry: | |||
# the third component of DIRECTION_OF_DETECTOR_X-AXIS= is sin(2theta), let's call this S2T. | |||
# in the right-angled triangle of crystal, (ORGX,ORGY), and (Xbeam,Ybeam), we can find the distance (ORGX-Xbeam) by taking tan(2theta)*|DETECTOR_DISTANCE|/QX . | |||
# now since sin(2theta)~tan(2theta) we can approximate the adjustment by S2T*|DETECTOR_DISTANCE|/QX | |||