The angular distance of an object below the horizon when it appears to lie on the horizon. The value 34′ is used in calculating rising and setting times given in The Astronomical Almanac.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。