Analysing Errors of Experimental Measurement and Theoretical Simulation of the Sun's Visual Shape

Atmospheric refraction and Special Relativity are the main reasons for the variation in visual shape of the Sun and make the Sun's visual shape always an ellipse. This paper analyses experimental errors due to an adjustment angle of the measurement camera and simulation errors due to neglecting the atmospheric influence on horizontal angle of view of the Sun and the fact that the Sun's velocity relative to the Earth is not perpendicular to the vector from the Earth to the Sun. First, the camera's adjustment angle is calculated, and the influence of the angle on experimental errors is evaluated. Second, the variation in the horizontal angle of view of the Sun, due to atmospheric refraction, is simulated through an iterative algorithm for tracing rays of light, and the influence of the angle variation on the Sun's visual shape is discussed. Finally, the fact, due to Special Relativity, that the contraction direction of the Sun's visual shape is not parallel to the CCD plane of the camera, is considered, and the maximum error due to neglecting the fact is evaluated. Results show that, for the observation point Dalian, the errors of experiment and simulation are very little and can be neglected.