Miscellanea Curiosa, Vol. 1: Containing a collection of some of the principal phaenomena in nature, accounted for by the greatest philosophers of this age
History
Miscellanea Curiosa, Vol. 1: Containing a collection of some of the principal phaenomena in nature, accounted for by the greatest philosophers of this age
Natural history; Science -- Early works to 1800; Voyages and travels -- Early works to 1800
Tab. 3. Fig. 6. Let T represent the Earth, TS, a Right Line joining the
Earth and Sun, TACB, a Right Line drawn from the Earth to the middle or
mean Place of the Moon's Apogee, equated, as above: Let the Angle STA be
the Annual Argument of the aforesaid Apogee, TA the least Eccentricity
of the Moon's Orbit, TB the greatest. Bissect AB in G; and on the Centre
C, with the Distance AC describe a Circle AFB, and make the Angle BCF =
to the double of the Annual Argument. Draw the Right Line TF, that shall
be the Eccentricity of the Moon's Orbit; and the Angle BTF, is the
second Equation of the Moon's Apogee required.
In order to whose Determination, let the mean Distance of the Earth from
the Moon, or the Semi-diameter of the Moon's Orbit, be 100000; then
shall its greatest Eccentricity TB be 66782 such Parts; and the least
TA, 43319. So that the greatest Equation of the Orbit, _viz._ when the
Apogee is in the Syzygys, will be 7 degrees, 39 minutes, 30 seconds, or
perhaps 7 degrees, 40 minutes, (for I suspect there will be some
Alteration, according to the Position of the Apogee in _Cancer_ and
_Capricorn_.) But when it is Quadrate to the Sun, the greatest Equation
aforesaid will be 4 degrees, 57 minutes, 56 seconds; and the greatest
Equation of the Apogee, 12 degrees, 15 minutes, 4 seconds.
Having from these Principles made a Table of the Equation of the Moon's
Apogee, and of the Eccentricities of her Orbit to each degree of the
Annual Argument, from whence the Eccentricity TF, and the Angle BTF
(_viz._ the second and the principal Equation of the Apogee) may easily
be had for any Time required; let the Equation thus found be added to
the first Equated Place of the Moon's Apogee, if the Annual Argument be
less than 90 degrees, or greater than 180 degrees, and less than 270;
otherwise it must be subducted from it; and the Sum or Difference shall
be the Place of the Lunar Apogee secondarily equated; which being taken
from the Moon's Place equated a third time, shall leave the mean Anomaly
of the Moon corresponding to any given Time. Moreover, from this mean
Anomaly of the Moon, and the before-found Eccentricity of her Orbit, may
be found (by means of a Table of Equations of the Moon's Centre made to
every degree of the mean Anomaly, and some Eccentricities, _viz._ 45000,
50000, 55000, 60000, and 65000) the _Prostaphæresis_, or Equation of the
Moon's Centre, as in the common way: And this being taken from the
former Semi-circle of the middle Anomaly, and added in the latter to the
Moon's Place thus thrice equated, will produce the Place of the Moon a
fourth time equated.
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