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Finding out ORGX ORGY: Difference between revisions
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There are different possibilities to find out where the direct beam would hit the detector: | There are different possibilities to find out where the direct beam would hit the detector: | ||
# visualize BKGINIT.pck, or FRAME.pck ( | # visualize BKGINIT.pck (from INIT), or FRAME.pck (from COLSPOT) with [[VIEW]], and click (left-mouse) into the middle of the beamstop shadow (or the attenuated direct beam itself, if it is recorded). Use the pixel coordinates displayed by VIEW as ORGX ORGY (in principle you should add 1 to both numbers, because for VIEW the pixels go from 0 to NX-1 whereas for XDS they go from 1 to NX).<br />Instead of these files written by XDS, one could directly use a measured frame. However this requires that one enters NX, NY, and the size of the header (which usually is <size of frame in bytes>, minus 2*NX*NY). | ||
# use adxv for visualization. Otherwise the same as with VIEW. (works for the PILATUS at SLS) | # use adxv for visualization. Otherwise the same as with VIEW. (works for the PILATUS at SLS) | ||
# use MOSFLM for visualization. It prints out X BEAM and Y BEAM from the frame header, and you may click on the hypothetical direct beam position. However, ''x and y are swapped in MOSFLM when compared to XDS'', and the coordinates are in mm, not in pixels. Sometimes the X BEAM and Y BEAM from the header are not reliable. | # use MOSFLM for visualization. It prints out X BEAM and Y BEAM from the frame header, and you may click on the hypothetical direct beam position. However, ''x and y are swapped in MOSFLM when compared to XDS'', and the coordinates are in mm, not in pixels. Sometimes the X BEAM and Y BEAM from the header are not reliable. | ||
# use ice rings to find out where the direct beam would be. This should be rather accurate but may be tedious. | # use ice rings to find out (in VIEW, and with paper and pencil) where the direct beam would be. This should be rather accurate but may be tedious. | ||
The error you make in the determination of ORGX ORGY should be less than half of the distance between two spots. If you have a reasonable estimate, 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.'' | ||
--[[User:Kay|Kay]] 15:03, 9 November 2007 (CET) | --[[User:Kay|Kay]] 15:03, 9 November 2007 (CET) | ||