Research On Seeing At Lijiang 2.4m Optical Telescope

Seeing,as one of the most important parameter for observatory selection and astronomical observation,is processed comprehensively and deeply by researchers.Because of the good astronomical condition including good Seeing,low atmospheric extinction and low night luminosity at the Lijiang observatory,the Lijiang 2.4m optical telescope was becoming an important platform for astronomical research in China.Dome structure and inner telescope's instruments will bring local turbulence in the surrounding of the mirror.This effect is called Dome Seeing and it will lead to image degradation.Considering the good local Seeing condition,Windows-Blinds and other hardware were built,but Dome Seeing were not measured for long-term.As well as observing strategy like central wavelength,altitude,focus choice,Dome Seeing will affect the measured FWHM in the terminal,and it will also affect the high-resolution imaging and measuring efficiency.Under the certain condition of observatory,telescope behavior and the instrument integration,Dome Seeing and observing strategy will affect the final Seeing.Based on the embedded STM32 system and RS485 network,Micro-Thermometry is designed to measure the atmosphere parameter directly called structure constant of the refractive index(²),which can calculate the seeing through its path integrals.On the other hand,the old manually-operated Windows-Blinds of dome are transformed.Because manipulating the Windows-Blinds will not only bring the new turbulence and will also cost the valuable observation time.After the transformation,it can be controlled more automatically and accurately based on the Dome Seeing value and outer weather condition.All those measure are used to reduce the wind vibration and the dome seeing's affect at the Lijiang 2.4m telescope.The different Seeing data are contracted with DIMM,Micro-Thermometry and FWHM methods to analyze the influence factors.The research of Seeing at the Lijiang 2.4m telescope in this article,can provide some constructive suggestions for Seeing improving and astronomical observation.