Fig. 1. Structural configuration of large telescopes

Fig. 2. Schematic diagram of three-axis error

Fig. 3. Schematic diagram of pointing error caused by parallax error

Fig. 4. Schematic diagram of pointing error caused by elevation axis error

Fig. 5. Schematic diagram of pointing error caused by azimuth axis error

Fig. 6. Comparison of harmonics at all levels of azimuth angle measurement error and correction

Fig. 7. Schematic diagram of the influence of gravity field on the deflection of the mirror tube

Fig. 8. Schematic diagram of pointing error caused by atmospheric refraction

Fig. 9. Comparison of azimuth pointing error before and after correction

Fig. 10. Comparison of elevation pointing error before and after correction