Predicting Weather By The Moon - Xavier University Libraries

Declination
month out, year in and year out as the monthly ‘declination
cycle’. It gets complicated, as this cycle itself undergoes
a gradual change.
We can think of it starting around AB. Let’s call that
the low-point. The Moon wobbles around the Earth all year,
about 13 times. After a year of such monthly declinations,
it has changed slowly, by 1°, either north or south depending
on were it is in the cycle. That means the declination
angle changes 1/13° or 0.08° per month. So after a year it
has risen up into a slightly bigger wobble - still crossing
AB to go underneath, still circling the Earth once per month
with a northern and southern declination and two equatorial
crossings. But its range of movement to the north and
south along the eastern horizon is now slightly more than
it was the previous year.
Suppose BOD is already at low - point, This in angles
is 18° above and below the equator each month(because
the Earth’s tilt is 23° and the Moon’s minimum declination
angle is 5° from the ecliptic(actually 5.145396° ). The last
time the Moon was at its 18° declination point occurred
on 16/3/97. After 9 years, after adding a degree per year,
the new monthly declination is 28° above and below the
equator - the maximum possible monthly declination. The
last high end was 29/9/87, which is when scientists first
coined the term ‘Greenhouse Effect’. At 1° added per year,
we will reach the upper level again in 22/3/06. 223 declinations
is the whole cycle.
As seen from the centre of the Earth the Moon drifts
up and down slightly more than 5° in the course of each
orbit. That’s because the Earth swings a little too, due to
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