Astronomy Explained Upon Sir Isaac Newton's Principles: And made easy to those who have not studied mathematicsFerguson, James
Science
Astronomy Explained Upon Sir Isaac Newton's Principles: And made easy to those who have not studied mathematics
Ferguson, James
Astronomy -- Early works to 1800
IV. But, (as it will sometimes happen) if the number of days fall short
of all those under the given Month, add one Lunation with its Anomalies
from Table VI to the foresaid sums; so you will have a new sum of days
wherewith to enter the 7th Table under the given Month, where you are
sure to find that sum the second time, if the first falls short.
V. With the Signs and Degrees of the Sun’s Anomaly enter Table VIII,
_The Moon’s annual Equation_, and take out the minutes of time of that
Equation by the Anomaly; remembring, that if the Signs are at the head
of the Table, the degrees are at the left hand, in which case the
Equation found in the Angle of meeting must be subtracted from the mean
time of New or Full Moon, as the title _Subtract_, at the head of the
Table directs: but if the Signs are at the foot of the Table their
degrees are in the right-hand column, and the Equation where the Signs
and Degrees meet in the Table is to be added to the mean time, as the
title _Add_, at the foot of the Table directs; which Equation, so
applied, gives the mean time of New or Full Moon corrected.
VI. With the Signs and Degrees of the Sun’s Anomaly enter Table IX,
_Equation of the Moon’s mean Anomaly_, and take out the Equation
thereof; adding it to the mean Anomaly or subtracting it therefrom, as
the titles at the head or foot of the Table direct; and it gives the
mean Anomaly corrected. Then, with the Sun’s Anomaly enter Table XII,
_Equation of the Sun’s mean Place_, and take out that Equation, applying
it to the Moon’s corrected Anomaly as the titles direct; and it will
give the Moon’s Anomaly equated[77]. _N. B._ In all these Equations,
care must be taken to make proper allowance for the odd minutes of
Anomaly; the Tables having the Equations only for compleat Degrees.
VII. With the Moon’s equated Anomaly enter Table X, _The Moon’s elliptic
Equation_, and take out that Equation in the same manner as the
preceding: adding it to the former corrected time if the Signs be at the
head of the Table, or subtracting it if they be at the foot, as the
Table directs; and this gives the mean time equated.
VIII. Lastly, enter Table XI, _The Sun’s Equation at New and Full Moon_,
with the Sun’s Anomaly, and take out the Sun’s Equation in the same
manner as the others; adding it to, or subtracting it from the former
equated time, as the titles direct: and by this last Equation you have
the true time of New or Full Moon, agreeing with well regulated Clocks
and Watches. But to make it agree with true Sun-Dials, the Equation of
time must be applied as taught § 225.
EXAMPLE I.
_To find the time of New Moon in_ April 1764, _N. S._
Public-domain text, read in full here on John Shaqi.
Reviews
Reviews
No reviews yet
Be the first to share your thoughts on this work.
Elsewhere in the archive
Join the Discussion
Join the discussion
Sign in to leave a comment or review.
Sign InorCreate an account