《明史·志·卷十三》
将这一天月亮的经度，减去前一天月亮的经度，如果是在午后望的，减第二天月亮的经度。余数是月亮的日运行度数。又将这一天正午太阳的经度，减去前一天正午太阳的经度，如果在午后望的，减第二天太阳的经度。余数是太阳的日运行度数。
求食甚凡时置其日太阴经度内减六宫，以减其日午正太阳度为午前望。置相减馀数相通秒，以二十四乘之为实，置其日太阴经度，内减前一日太阴经度，馀为太阳日行度。
Subtract the lunar longitude of this day from that of the previous day; if observed in the afternoon, subtract the lunar longitude of the following day. The remainder is the lunar daily motion in degrees. Subtract the solar longitude of this day at noon from that of the previous day at noon; if observed in the afternoon, subtract the solar longitude of the following day. The remainder is the solar daily motion in degrees.