An interference figure produced looking straight down or close to the optic axis of a uniaxial mineral will show a characteristic [[Maltese cross|"Maltese" cross]] shape to its isogyres. If you are looking perfectly down the optic axis, the pattern will remain completely unchanging as the stage is rotated. However, if the viewing angle is slightly away from the optic axis, the centre of the cross will revolve/orbit around the central point as the stage is rotated. The form of the cross will stay constant as it moves.
