The Kossel technique is known due to its precision for lattice constant determination in micro ranges by use of X-ray films. Recently we observed the Kossel interferences also by a CCD camera in a good quality. Thus, the diffraction interferences could be immediately processed and evaluated by computer permitting considerable time saving. In order to obtain the similar accuracy as for measurements with X-ray films further technical and experimental improvements were necessary, especially for a better contrast to observe intersection points of several weak reflections, for evaluating digital patterns, for optimizing of the shortest focus-screen distance and for considering the image field curvature of the objective. As a result, a precision in lattice constant determination could be achieved at a Fe-crystal coming relatively close to the one of comparable X-ray film patterns, which is still about one order of magnitude better for the time being.