CHAP. 30. To find the visible motion of the Moon from the Sun for any time assigned.
AT the beginning and end of the time proposed find the parallax of the Moone from the Sun in Longitude, and then observe these rules.
- 1 If during all the time proposed, the luminaries be in the ori∣entall quadrant, and the parallax of longitude increase or be greater at the end of the time given then at the beginning, adde the differences of the two parallaxes of longitude unto the true motion of the Moone from the Sun agreeing to the time given, or if it decrease, subtract it and you have what you desire.
- 2 If during all the time the luminaries be in the occidentall quadrant, and the parallax of longitude increase, subtract the said difference from the true motion, if it decrease, adde it, and you have the visible motion.
- 3 If at the beginning of the time the luminaries be in the orientall quadrant, and at the ending in the occidentall, subtract the said diffe∣rence from the true motion, and you have the visible motion during that time.
Example.
Let it be proposed to find the visi••le motion of the Moon from the Sun, for one halfe hour before the true Conjunction.
- In our Example, the true halfe hourly motion is
- . 28070
- Parallax of Longitude at the beginning
- . 07628
- Parallax of Longitude at the end
- . 02243
- Their difference is Subtract
- . 05385
- from the true halfe hourly motion Rests
- . 22658
the visible halfe hourly motion before the Conjunction.