天文实测蒙气差的研究

建立在子午—卯酉交替观测原理基础上的低纬子午环（ＬｏｗＬａｔｉ－ｔｕｄｅＭｅｒｉｄｉａｎＣｉｒｃｌｅ）即将出厂投入调试及试运行阶段，进一步研究天文蒙气差修正将是低纬子午环进行高精度观测的重要保证之一。作为对天文蒙气差修正的初步研究，本文首先分析了影响天文蒙气差的主要气象因素，对蒙气差随各种条件的变化情况进行了讨论；在此基础上，推算了大气平面平行层模型以及同心球层模型下的蒙气差值，论述了蒙气差表的编制方法，进而对各种蒙气差理论公式计算所得的修正值进行了分析比较；针对理论计算蒙气差值精度的不足，本文着重阐述了利用低纬子午环（ＬＬＭＣ）进行大气蒙气差实测的方法、原理，较为详尽的说明传统的方法不能满足实测大气折射的要求，而低纬子午环由于自身一些新的特点，能够满足Ｔｅｌｅｋｉ所提出的四个要求；在此基础上推导了相应的计算公式并进一步探讨了实测大气等密度倾斜的方法，最后给出了相应的精度估计，就如何建立一个适合于观测点的实用的实测大气模型进行了探讨

Research on the Actual Measurement of Atmospheric Refraction

Low Latitude Meridian Circle(LLMC)will soon enter the period of testing and experiment. It is well kown that atmospheric refraction is the most important factor for astrometric observation. In order to get the high accuracy results, atmosphere refraction should be considered carefully. In the first part of this thesis paper, we have introduced the classic theories and processing mothods of the atmospheric refraction. At first, we have analyzed some important meteorological factors that may influence the value of atmospheric refraction in astronomy and argued the change of the atmospheric refraction accompanied with all kinds of conditions. Second , we have derived the formula and calculated the value of atmospheric refraction in two ideal atmosphere models and then presented the method of compiling atmospheric refraction table in astronomy. In the second part, we have analyzed the four conditions and explained that the classical theory can not fit for the conditions. Then we have introduced advantages of the LLMC and proved that the LLMC will be suitable for the four conditions very well. Finally we express the method and principle of actual measurement of atmospheric refraction and derive some formula.