Fig. 1. Simulation results of focal length changes of different spectral bands with temperature

Fig. 2. Relationship between temperature and focal length. (a) Linear-convex curve model; (b) convex curve-linear model; (c) convex curve-concave curve(or linear)-concave curve model; (d) convex curve model; (e) concave curve-convex curve(or linear)-convex curve model; (f) convex curve model

Fig. 3. Relationship between the temperature and the change of the Cassegrain focus for the 1 m telescope

Fig. 4. Simulation result of linear compensation model

Fig. 5. Simulation results of Fourier compensation model. (a) Simulation result of the first-order Fourier compensation model; (b) simulation result of the second-order Fourier compensation model; (c) simulation result of the third-order Fourier compensation model

Fig. 6. Experimental simulation results. (a) Fitting result (up) and residual(down) of linear compensation model; (b) fitting result(up) and residual(down) of Fourier compensation model

Fig. 7. Residual comparison of two compensation models