《明史·志·卷十一》
推算夜半赤道宿度：取夜半赤道积度，用赤道宿度依次相减，就是本日夜半的赤道宿度。
推夜半赤道宿度置夜半赤道度，以赤道宿度挨次减之，为本日夜半赤道宿度。
Deduce the equatorial station of midnight: the equatorial accumulated degree at midnight, subtract the equatorial station degree, the equatorial station at midnight on this day.