Astronomical Observing Conditions Of Xinglong Observatory And Performance Enhancement

Monitoring and analyzing for ground-based optical site observing conditions is a long-term and complicated scientific research work. For new astronomical site, the quality and consistency of observing conditions directly decides the selection of equipments, construction of telescopes, and scientific output. It is also important for existing astronomical site, Especially for Monitoring meteorological conditions, number of photometric nights and spectroscopic nights, night sky brightness, astronomical seeing, and other parameters, in order to optimize the equipment configuration and improve the scientific output.This thesis began with the influence of earth's atmosphere to the ground-based optical astronomical observations, and introduced the influence of different height of earth's atmosphere to astronomical observations. As the analysis for the ground-based astronomical site, we mainly introduced the famous ground-based optical astronomical site around the world, including geographical location, altitude, etc. and its typical optical telescopes. Further, we introduced the various parameters that are necessary to be monitored and analyzed for the ground-based astronomical site, and its research progress all around the world.We systematically discussed the various parameters of the astronomical ob-serving conditions, including the meteorological parameters:air temperature, relative humidity, air pressure, cloud cover, dust, wind speed and wind direction. We studied the relationship between the various parameters and the astronomical observations in detail. As the main parameter for available time, we focused on international definitions of photometric nights and spectroscopic nights, in order to provide the standard references for later analysis with Xinglong Observatory. As the key parameter of quantitative assessment to the atmospheric turbulence, we began with the definition of astronomical seeing, mainly introduced the differ-ent methods and instruments for monitoring and analysis it in different period, and compared its advantages and disadvantages. To understand the parameters that affect optical telescope equipments limiting magnitude and photometric ac- curacy, we analyzed the light pollution sources and different ways of monitoring the night sky, and the different monitoring methods around the world in different periods; In addition, we also introduced the atmospheric extinction and atmo-spheric scattering, and its influence to the astronomical observations, in order to lay the foundation for the following analysis.Xinglong Observatory of the National Astronomical Observatories, Chinese Academy of Sciences(NAOC), is one of the major optical observatories in China, has a history of nearly 50 years. This thesis is based on the archival data and the existing observation conditions, gives the analysis for the meteorological pa-rameters, number of photometric nights and spectroscopic nights, astronomical seeing, night sky brightness. Using the above data, we performed critical analysis of meteorological conditions at Xinglong Observatory, such as air temperature, relative humidity, wind speed and its directions, photometric nights and spectro-scopic nights and its change with the time, in order to provide a detailed reference data for key topic selection, time distribution, equipments maintenance, and its upgrade. This thesis studied astronomical seeing and its variation in differen-t months and seasons, and compared the seeing data obtained within the dome and outside, in order to provide reference for improving dome seeing conditions in future. This thesis presented the night sky brightness with different phases of the moon, different altitude angle and azimuth angle, and verified with photometric and spectroscopic measurements, in order to provide a quantitative reference for astronomers using Xinglong Observatory telescopes, and contribute to improve the observation strategy at the same time.This thesis finally discussed the change of observing conditions over time at Xinglong Observatory and compared with the observing conditions at various observatories around the globe. Based on the existing conditions of Xinglong Observatory, we put forward a series ways to improve the performance of tele-scopes, in order to upgrade the Xinglong Observatory equipments performance and scientific output with the combination of hardware and software.