多功能天文经纬仪光轴指向变化实测与修正

Measurement and calibration of optical axis changes for multi-function astronomical theodolite

光轴指向变化是地面天体测量误差最大来源之一,对光轴指向变化进行准确测量和修正是获取高精度天体测量数据的必要前提。针对云南天文台多功能天文经纬仪高精度时纬测量工作的需求,分析和测定了光轴指向变化对时纬测量的影响。首先,介绍了多功能天文经纬仪实时测定光轴指向变化的原理和方法,然后对望远镜光轴指向变化进行了实时测定和分析。实验结果表明,由于镜筒受重力的影响,相较于测时结果而言,光轴指向变化对测纬结果的影响更大。在天顶距为55°时,最大可以达到2.5″。经过光轴指向变化修正后,测纬精度由1.37″提高到了0.36″,测时精度由0.033 s提高到了0.023 s。通过分析光轴指向变化的实时测定结果可以看出时纬测量精度有了显著改善,基本满足高精度天体测量需求。

Telescopic Optical Axis Change(OAC)is the main source of systematic errors in astrometry.Real-time determination and calibration of OAC are the foundation for obtaining high-quality astrometric data.The determination and analysis of the influence of OAC on time and latitude measurements should be performed to meet the requirements of high-quality astrometric results.First,the influence of OAC on time and latitude measurements were analyzed.The method of determining OAC for multifunction astronomical theodolite was introduced.Then,we determined the OAC in real time and analyzed the results.The experimental results indicate that the influence of OAC on latitude measurement can reach to 2.5"when the zenith distance is 55°.The precision of latitude measurement can reach 0.36"from 1.37"after the calibration of OCA.The precision of time measurement can reach 0.023 s from 0.033 s after the calibration of OCA.The precision of latitude and time measurements significantly improved and can satisfy the requirements of high-quality astrometry after the measurement and calibration of OAC in real time.