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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: | ||
# use [[XDSGUI]] and load a frame. If you don't have XDS.INP, press the button generate_XDS.INP. There will be a green cross at ORGX,ORGY from XDS.INP. If that cross is not where you think it should be based on the beamstop shadow, just move the mouse to the correct position (middle of beamstop shadow), look at the X and Y position of the mouse in the upper right part of the panel, and transfer these values to XDS.INP, as ORGX and ORGY. When you go back to the Frame tab, the green cross should be at the correct position. | |||
# visualize BKGINIT.cbf (from [[INIT]]), or FRAME.cbf (from [[COLSPOT]]) with [[XDS-Viewer]], 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 [[XDS-Viewer]] as ORGX ORGY (in principle you should add 1 to both numbers, because for XDS-Viewer 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. (If XDS-Viewer does not know the format, it will ask for NX, NY, and the size of the header. The latter is usually <size of frame in bytes>, minus 2*NX*NY .) | # visualize BKGINIT.cbf (from [[INIT]]), or FRAME.cbf (from [[COLSPOT]]) with [[XDS-Viewer]], 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 [[XDS-Viewer]] as ORGX ORGY (in principle you should add 1 to both numbers, because for XDS-Viewer 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. (If XDS-Viewer does not know the format, it will ask for NX, NY, and the size of the header. The latter is usually <size of frame in bytes>, minus 2*NX*NY .) | ||
# use [[adxv]] for visualization. Otherwise the same as with XDS-Viewer. (1.9.7beta version works for the PILATUS detector at SLS) | # use [[adxv]] for visualization. Otherwise the same as with XDS-Viewer. (1.9.7beta version works for the PILATUS detector 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 (so one has to divide by QX). 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 (so one has to divide by QX when going from MOSFLM units to XDS units). Sometimes the X BEAM and Y BEAM from the header are not reliable. | ||
# use ice rings to find out (in [[XDS-Viewer]], and with paper and pencil) where the direct beam would be. This should be rather accurate but may be tedious. | # use ice rings to find out (in [[XDS-Viewer]], and with paper and pencil) where the direct beam would be. This should be rather accurate but may be tedious. | ||
# use the Unix command line tools to look at the header of the frame. E.g. "strings <frame-name>|more" would should you the (hopefully correct) information stored in the header, like wavelength, delta-phi, X and Y beamcentre and so on. | # use the Unix command line tools to look at the header of the frame. E.g. "strings <frame-name>|more" would should you the (hopefully correct) information stored in the header, like wavelength, delta-phi, X and Y beamcentre and so on. | ||
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 | 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 ORGX ORGY by inspecting [[IDXREF.LP]] . This works best if [[COLSPOT]] has seen a significant fraction of all frames.'' This procedure is [[Thaumatin_ACA2014#Digression:_a_computational_investigation_into_the_robustness_of_the_indexing|documented]]. | ||