Fig. 1. VT main body structure

Fig. 2. Partial connection structure of outer baffle，secondary mirror supporter and loader cylinder

Fig. 3. The secondary mirror component of VT

Fig. 4. Finite element model of the combination of outer baffle， secondary mirror components and loaded cylinder

Fig. 5. Secondary mirror displacement cloud map when the root of the outer baffle is 20 ℃ and other parts of the outer baffle are 19 ℃

Fig. 6. The impact of one end of the outer frame of the secondary mirror supporter being limited and the other end shrinking on the secondary mirror

Fig. 7. The displacement of secondary mirror at different temperature of the root of the outer baffle

Fig. 8. VT thermal equilibrium test design

Fig. 9. Implementation matters and photo of temperature control measures at the root of the outer baffle

Fig. 10. Overfocus curve of VT in thermal equilibrium test

Fig. 11. Changes in energy concentration at the fixed focal plane position during periodic temperature changes at the root of the outer baffle