Scheme of a solar image. The outer square shows the boundaries of a solar image from a spacecraft. The marker C at the top left corner indicates the pixel with the coordinates (1,1), i - row number, j - column number. The marker C’ also shows the pixel with the coordinates (1,1), but in a new coordinate system with rows i′ and columns j′ connected to i and j via Equation (A.6). “Top”/“Left” show the distance (in pixels) from the top/left border of the image to the beginning of the Sun. P is a pixel, and are the coordinates of its center.