天文定位中常用四参数模型进行坐标转换，在建立四参数模型时未考虑坐标尺度系数和坐标轴之间的夹角变化，因此四参数模型是天文定位中坐标转换的参数简化模型。为了验证四参数简化模型的适用性，在四参数简化模型的基础上建立了六参数模型。从模型建立角度上推导了四参数和六参数模型在定位精度和倾角补偿上的差异性，并对两种模型进行了比较。实验数据的分析结果表明两种模型在天文定位的精度上基本一致，也证明了四参数简化模型的适用性。

The four-parameter model is often used in astronomical fixation,but the coordinate scale and change of the angle between the coordinate axis are not taken into consideration.Therefore,the four-parameter model is only a simplified model for coordinate transformation of astronomical fixation.In order to verify the applicability of the model,and improve the precision when dealing with the transition between the tangential coordinate and the CCD image coordinate,a six-parameter model was built up based on the four-parameter model.Contrastive analysis was made to the two models in the aspects of positioning accuracy and tilt angle compensation.The analysis result to data obtained from the experiments demonstrated that the two models have basically the same precision,thus the applicability of the four-parameter model was proved.