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
The greatest Variation of the Moon (_viz._ that which happens when the
Moon is in an Octant with the Sun) is nearly, reciprocally as the Cube
of the Distance of the Sun from the Earth. Let that be taken 37 minutes,
25 seconds, when the Sun is _in Perigæo_, and 33 minutes, 40 seconds,
when he is _in Apogæo_: And let the Differences of this Variation in the
Octants be made reciprocally, as the Cubes of the Distances of the Sun
from the Earth; and so let a Table be made of the aforesaid Variation of
the Moon in her Octants (or its Logarithms) to every Tenth, Sixth, or
Fifth Degree of the mean Anomaly: And for the Variation out of the
Octants, make, as Radius to the Sine of the double Distance of the Moon
from the next Syzygy, or Quadrature :: so let the afore-found Variation
in the Octant be to the Variation congruous to any other Aspect; and
this added to the Moon's Place before found in the first and third
Quadrant (accounting from the Sun) or subducted from it in the second
and fourth, will give the Moon's Place equated a fifth time.
Again, as Radius to the Sine of the Summ of the Distances of the Moon
from the Sun, and of her Apogee from the Sun's Apogee (or the Sine of
the Excess of that Summ above 360 degrees,) :: so is 2 minutes, 10
seconds, to a sixth Equation of the Moon's Place, which must be
subtracted, if the aforesaid Summ or Excess be less than a Semi-circle;
but added, if it be greater. Let it be made also, as Radius to the Sine
of the Moon's distance from the Sun :: so 2 degrees, 20 secants, to a
seventh Equation; which when the Moon's Light is increasing, add; but
when decreasing, subtract; and the Moon's Place will be equated a
seventh time, and this is her Place _in her proper Orbit_.
Note here, the Equation thus produced by the mean Quantity 2 degrees, 20
seconds, is not always of the same magnitude; but is increased and
diminished, according to the Position of the Lunar Apogee. For if the
Moon's Apogee be in Conjunction with the Sun's, the aforesaid Equation
is about 54 seconds greater: But when the Apogees are in Opposition,
'tis about as much less; and it librates between its greatest Quantity 3
minutes, 14 seconds, and its least, 1 minute, 26 seconds. And this is,
when the Lunar Apogee is in Conjunction, or Opposition with the Sun's:
But in the Quadratures, the aforesaid Equation is to be lessen'd about
50 seconds, or 1 minute, when the Apogees of the Sun and Moon are in
Conjunction; but if they are in Opposition, for want of a sufficient
number of Observations, I cannot determine, whether it is to be lessen'd
or increas'd. And even as to the Argument or Decrement of the Equation,
2 minutes, 20 seconds, above mentioned, I dare determine nothing
certain, for the same Reason, _viz._ the want of Observations accurately
made.
Public-domain text, read in full here on John Shaqi.
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