Realization of solar corona polarimetry pertains to astrophysical centre-symmetrical problems. Usual ways of digitization are not optimum for this task. Coronal images obtained during solar eclipse at different angles of the polarizer should be digitized symmetrically in relation to the centre of the solar disk. Unfortunately, digitization of such centre-symmetrical images is usually performed by rectangular scanning with a firmly oriented digitization slit. Corresponding pixels in different images have to be found by methods of shifting the centres of the relevant images and a necessary rotation of the images. When the images are almost identical, or at least very similar each to other, the final fitting of the images can be tested by calculating the best correlation. As a rule, this is not the case for solar corona images obtained with different angle of the polarizer. In addition, after rotation of the digitized image, the digitisation rectangular networks become incompatible and thus some information is changed or even lost.