The prediction of spot positions on equi-inclination Weissenberg photographs

An algorithm is presented for using equi-inclination Weissenberg and precession photographs to index an unknown triclinic cell to give a right-handed homogeneous vertex at the origin. Using such indexing, and known crystal parameters and camera settings, the geometry of reflexion is analysed to predict spot positions on both halves of equi-inclination Weissenberg photographs.