在利用分光计测量三棱镜折射率的实验中，一个关键的步骤是调整载物台使其主轴和望远镜、平行光管主轴相互垂直.这种情况被称为标准情况.对于实验中存在的载物台偏离标准情况，本文从理论和实验上分析了其对顶角和最小偏向角测量的影响.实验上分两种情况进行了测量，一种情况是: 平面镜至少一面反射的绿十字像落在视野内，此时用绿十字像的位置标定载物台的倾斜程度; 另一种情况是: 外置一个测量载物台主轴俯仰角的实验装置，用偏离角度描述载物台的俯仰程度.本文测量了两种情况下三棱镜顶角和最小偏向角随载物台倾斜的变化，得到了小于测量本身误差对应的载物台倾斜范围.

In the experiment of measuring the refractive index of a prism with a

spectrophotometer，a key step is to adjust the object stage so that its main axis is perpendicular

to the optical axes of the telescope and the collima- tor，which is called the standard case. It is

analyzed that the influence on the measurement of apex angle and mini- mum deviation angle

theoretically and experimentally when there is a deviation of the object stage. The experiments are

performed for two cases. One case is that，in the telescope，it can be found that a green

cross image reflectes from at least one surface of the double face plane mirror. In this case，the

deviation is marked by recording the posi- tion of the green cross image. The other case is that

the deviation of the object stage is measured with an extra sys- tem. In this case，the deviation

degree of the object stage can be recorded directly. In experiment，the variation of the apex angle

and minimum deviation angle of the prism with the deviation of the object stage is measured

in the two cases. And the object stage’s deviation range，at which the experimental

results has smaller deviations than standard measurement errors，is determined.