On refinement of the crystal orientation matrix and lattice constants with diffractometer data. II

A modification of the refinement procedure proposed by Shoemaker & Bassi [Acta Cryst. (1970). A26, 97] is described in which the correction to the unitary orientation matrix, valid to second order in the small rotational adjustment, is applied after constraints due to crystal symmetry (which is presumably lost owing to measurement errors) have been applied to the lattice constants, and in such a way as to preserve (to second order) the unitary character of that matrix.