Retrieval errors of the atmospheric composition using optical methods (DOAS et al.) are under the determining influence of the cloudiness during the measurements. If there is information about the clouds, the optical model of the atmosphere used to interpret the measurements can be adjusted, and the retrieval errors are reduced. For the reconstruction of the parameters of clouds a method was developed based on taking pictures of the sky by a pair of cameras and subsequent processing of the obtained sequence of stereo of frames by a method of morphological analysis of images. Since the directions of the optical axes of the cameras are not exactly known, the graduation of the direction of sight of the cameras was conducted at the first stage using the photographs of the stars in the night sky. As a result, the coefficients of the affine transformation relating own coordinate systems of the cameras were determined. The authors have confined themselves to affine transformations, as the angle between the optical axes was small enough, and the corresponding points on the stereo pair were chosen near the optical axis. At the second stage, the relative shift of the image of the cloud fragment on the second frame of the pair was calculated. Stereo pairs obtained by simultaneous photography, allowed us to estimate the height of cloud. The paper poses and solves the problem of graduation of direction of sight of the cameras, shortly describes the main features of other steps of the method of estimating the height of cloud base. The examples of first evaluations in a real photo are analyzed.