NavList:

From George- There's a bit more to add, about the Moon, which may be
of interest.

Near the spring equinox, the Moon will ride high in the sky (about as
high as the summer Sun would) around first quarter, when it's about 7
days old. That applies in both hemispheres (due to the different date
of local spring). It will be low (low enough to be invisible all the
time from Thule, Greenland) around last quarter.

And conversely, of course, at autumn equinox.

But in comparing the height of a winter full Moon with the height of
the summer Sun (for example), we have all been careful to say that
they are "approximately" equal. Only approximately so, however; the
differences are rather significant.

For a few years at a time, the Moon, in its monthly path, swings
between North and South declinations that are significantly greater
than the 23.5 degrees North and South of the Sun. Just this year, it's
been at the maximum of that swing,  being about 28.5 degrees North and
South. So this year, the Moon, when at its highest, (full in winter,
or last-quarter in autumn) gets into parts of the sky that the Sun
never reaches; 5 degrees higher, indeed. And when the Moon's crosses
the meridian at its lowest ( when full in summer, or at first-quarter
in autumn) it is significantly nearer the horizon than you will ever
see the winter noon Sun get, by all of 5 degrees. That difference is
significant, and noticeable.

Already, though, those wild swings of the Moon have just started to
draw in from their maximum value. By late 2011, they will be no
greater than that of the Sun. By late 2015, the Moon will cover a much
more restricted range of declinations than the Sun, between 18.5
degrees North and South. And in 2025, it will be back to its maximum
swing once again.

Why should this be? It's one of the effects of precession, at its most
dramatic. The Sun sticks, rather strictly, to the constant plane of
the ecliptic. Of course, in reality, it's the Earth sticking to that
plane in its orbit round the Sun, even if we like to think of it the
other way round. And it's the tilt of the Earth's equator, by 23.5
degrees, to that plane, that gives us our seasons.

The Moon's plane, in its orbit around the Earth, is near the plane of
the ecliptic, but not on it, being tilted by about 5 degrees. And the
direction of that tilt isn't constant, but gradually wanders in a
circle, taking nearly 19 years to do so. Sometimes that tilt is in a
direction so as to enhance its angle to the Earth's equator, to28.5
degrees, as of now. Other times, it detracts from it, to about 18.5
degrees.

Precession of the plane of the Moon's orbit is the consequence of the
subtle interaction of the gravitational fields of the Earth and the
Sun, both of which influence its path.

George.

contact George Huxtable at george@huxtable.u-net.com
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.

==================================

Previous discussion about the winter Moon in the above the Arctic
circle has been-
|
| Yes, that's correct.  It doesn't get very high, however, because of
| the latitude, and is too dim to burn through much of a cloud layer.
| When it's full, it gets highest around 12 midnight or thereabouts.
|
| Fred
|
| On Aug 30, 2006, at 6:23 PM, coralline algae wrote:
|
| > Assuming a visible full moon in thule, greenland
| > then it will be above the horizon  most of the days hours
| > even though the sun itself never rises.   In the perpetual
| > darkness of winter near the poles, the full moon provides
| > a partial respite.    Actually this is a guess on my part
| > but then the logic seems sound.
| >
| >
| > On 8/30/06, Bill Noyce < wbnoyce@gmail.com> wrote:
| > My bedroom window faces south, and I've often been struck by
| > how high the full moon gets in the winter.  Since it stays near
the
| > ecliptic, the winter full moon will have a declination near that
of
| > the summer sun, and vice versa, as Fred points out.  First and
| > last quarter moon on the solstices should be near zero
declination.
| >     -- Bill
| >
| > On 8/29/06, Fred Hebard <Fred@acf.org> wrote:
| > >
| > > It depends on the phase of the moon.  When it's opposite the
sun,
| > > full, it's declination is approximately the inverse of the sun's
| > > declination.  For instance, on June 21 (summer solstice), the
sun is
| > > at approximately 23 N and the moon at approximately 23 S, if the
| > moon
| > > is full on that date.  Clearly, inverse is not the correct term
for
| > > this relationship, but....
| > >
| > > Fred


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