中国科学院南京天文光学技术研究所机构知识库

Atmospheric dispersion has a great impact on high-precision astronomical observation. This paper studies the influence of atmospheric dispersion on the imaging system of large aperture astronomical telescope, and the UMAC-based atmospheric dispersion correctors (ADC) control system is designed. According to the data of zenith distance, temperature, humidity and air pressure, the influence of atmospheric dispersion on the imaging system of the telescope is calculated through the theoretical model of atmospheric refraction. The results show that when the zenith distance is greater than 24.83°, the influence of atmospheric dispersion has exceeded 0.3”,that is the requirement of telescope imaging system. So it is necessary to correct the influence of atmospheric dispersion. ADC adopts the structure of two relative rotation glued prisms. The larger the zenith distance is, the higher the requirement of the relative angle control accuracy of the two glued prisms is.

According to the results of optical calculations, when the relative rotation accuracy of the two glued prisms is less than 60”, it can meet the imaging quality requirements of the telescope. According to that, the control system of ADC is designed.

The rotation control of atmospheric dispersion correction mechanism adopts two-stage reduction mechanism, thefirst stage is reduction box, the second stage is reduction gear, and the total reduction ratio is 600:1. In order to realize the synchronous control of the two glued prisms, UMAC is used as the main controller, two servo motors are used to drive the rotation of the two glued prisms, and Renishaw encoder is used as the position feedback for position closed-loop control. The peak-to-peak control accuracy of the relative rotation angle of the control system is less than 20”, which meets the control accuracy requirements of the ADC.