Determination of astronomic azimuth by measuring the Sun's angular elevation, the angle of the marker from the Sun at that instant and the time of measurement. The formula is cot²(½ A _s) = (sin½ (S - φ_a) sin(S + θ))/(cos S cos (S + δ)). The Sun's azimuth is A_s, the astronomic latitude of the observer is φ_a, the zenith distance of the Sun is θ (90° - measured angular elevation), the Sun's declination at the instant of observation is δ and S is the quantity (ö_a - θ - δ). The azimuth of the Sun is added to the measured angle of the marker with respect to the Sun to get the azimuth of the marker.