Chi is the azimuthal angle angle that defines the orientation of a feature in an image.
By default, chi=0 is defined to be in the usual place, at the bottom of the first quadrant.
This is fine for powder diffraction patterns or other cases where the orientation does not matter.
However, suppose you have a fiber that is almost but not quite aligned with the horizontal or vertical axis.
In that case you might want to make qx-qy plots, or to define chi=0 to be along the fiber axis.
Datasqueeze deals with this by redefining the meaning of "chi=0". The "chi offset"
is the amount in degrees by
which the experimental equator differs from the nominal horizontal direction. To set it:
- Click on Set Chi Offset. A crosshair pattern should appear in the false color image.
- You can either type your best estimate for the chi offset into the box, or drag the
control points on the cross hair until a horizontal or vertical line is aligned with an
interesting feature in your data.
- Click on Done.
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