能见度对天体观测高度的影响

为降低海上能见度条件对天文定位的限制,开展能见度对天体观测高度的影响研究。通过数学推导得出能见度小于理论视距时观测高度的修正计算式;在此基础上,考虑地面折光差的影响,提出观测高度的实际修正计算式并将其编制成方便查算的表格。能见度引起的观测高度修正量与观测者眼高和海上能见距离两种因素有关,随观测者眼高的增高而增大,随海上能见距离的增大而减小。将研究结论应用到海上太阳高度的实测中,结果表明:该方法能提高能见度小于理论视距时天体高度观测的准确性,可为不同能见度条件下的天体观测高度修正提供定量依据。

Influence of Visibility on Altitude Observation of Celestial Body

To reduce visibility limitation in celestial navigation at sea,the study on the influence of visibility on altitude observation of celestial body is set out.A formula is derived for correcting the altitude observation taken when the visual range is less than the theoretical visibility.The effect of ground refraction is taken into account,the final correction formula is derived and the easy-to-check correction table lists are compiled.The study shows some relationship that the correction value of observed altitude increases with the increase of the height of eye,and decreases with the increase of the visible distance at sea.The method is verified with solar altitude observation at sea,proving a quantified reference for different visual range observation,and can increase observation accuracy when the visual range is less than the theoretical visibility.