Abstract: Researchers establish the equation of the curve described by the wave vector of the extraordinary wave on the second surface of the plane parallel piece cut from a uniaxial crystal with optical axis’s random orientation in relation to the normal to the piece, under the ray’s rotation around the normal (this ray descents at any constant angle onto the first surface). This helps to obtain and analyze, without any simplications, used in known works, the equation describing the form of isochromes of any order in conoscopic patterns of uniaxial crystals. The calculated isochromes patterns for some angles between axis and normal which have the most obvious difference from the ones which were prognosticated before are verified experimentally on paratellurite crystal with special orientations of two pairs of faces.