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--- dac_experiments:geometry [2019/06/07 17:01] – [Example: How to find out my own O-matrix] matthias
+++ dac_experiments:geometry [2026/08/12 05:35] (current) – smerkel
@@ Line 12: / Line 12: @@
 More precise and detailed calculations are available in this file, extracted from the fable project: {{ :processing:fable_geometry_version_1.0.8.pdf |}}.
+===== Omega rotation direction =====
+Pay attention to the direction of the omega rotation. On many beamlines, the direction of omega is opposite to the drawing above. Simple take a picture of your sample, with a negative omega value, a positive omega value, and cross-check.
+In the [[fileformat:prm|Input file for ImageD11 (prm)]], the omega rotation direction is defined with the parameter **omegasign**.
+If you are performing a DAC experiment, the shadows from the DAC opening can help to figure out whether your omega rotation axis is positive (as in the drawing above) or negative.
 ===== Detector orientation =====
@@ Line 32: / Line 40: @@
 Let's do it for the image at ω1 = -20°
+Images, such as the one below, can be generated with the [[software:timeless_viewer|TIMEleSS Viewer]].
 {{ :dac_experiments:orientations.png?600 |Fig. 3: Example for different orientations of the same image}}
-Fig. 3: Example for different orientations of the same image.
+Fig. 3: Example for different orientations of the same image. Those were generated in Fabian, but you can now get the same in the more modern implementation of the [[software:timeless_viewer|TIMEleSS Viewer]].
 === Step 1 ===