Both directions of the tilt now go through the same restraint, with a budget each in shared
direct-beam pixels; zero means free. Swapping which component is held, or holding both, is a change to
two constants. The perpendicular budget is zero today, which is the arrangement the measurements
support: it is the component whose conditioning tracks the 2theta the fit reaches, while the parallel
one's does not move with 2theta at all - a conditioning number that ignores the data is the prior
talking.
This is a clarity change, not a precision one, and the record should not read otherwise: the standing
'freeing the tilt inflates both beam components' cost is the perpendicular component's doing, not the
parallel one's, so restraining the parallel one recovers essentially none of it. What it buys is that a
beam-centre error is no longer reported as an angle.
leonarski_f
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