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Movements in momentum space are possible after the UB matrix has been setup. We begin by supplying the lattice parameters a, b, c, alpha, beta, gamma (e.g. 5.43, 5.43, 5.43, 90, 90, 90). This is easily done with the UbMatrix widget of Online (called from Online, Diff), see section 8.5.
The lattice parameters are written to the server by pressing 'UpdDiffSrv'. The UB matrix is automatically read-back. At this point it contains only the transformation from direct to reciprocal space, no rotations are taken into account so far.
The Alignement widget (called from Online, Diff), section 8.6, helps us during the orientation. Angular scans are used to find reflections. After two reflections have been found, the 'ComputeU' button of the UbMatrix widget computes the UB matrix and we are done.
In addition to the command 'ComputeU' which uses the lattice and two reflections there is the command 'Affine' which uses the simplex method to compute the lattice parameters and the U matrix. 'Afffine' needs more than 2 reflections as input.