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The heated air formed inside a solar telescope due to solar radiation will warm up the mirror surface, and local atmospheric turbulence will be generated above the mirror surface, which will cause the mirror seeing and thus the serious attenuation of image quality. In this paper, based on the theory of atmospheric turbulence, we analyze the physical process of mirror seeing produced by turbulent shear airflow, and use the experimental data of 1550mm large diameter hyperboloid mirror to derive and verify the theoretical model of mirror seeing. The effect of the change of temperature difference between the mirror and the surrounding air on the mirror seeing was experimented under two conditions of free convection and forced convection, respectively, at different mirror wind speeds. The results show that it is clear that the temperature difference between the mirror surface and the surrounding air is strongly correlated with the seeing, and the mirror seeing can be reduced by increasing the active ventilation. The mirror seeing is 0.98" at free convection of 4°C, 0.20" at forced convection with low wind speed, and 0.12" at forced convection with high wind speed under a mirror-air temperature difference of 3°C. The research results aim to reveal the formation mechanism and propagation law of air turbulence and its influence on the image quality degradation of the telescope, and lay the foundation for improving the working resolution of the large solar telescope.
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