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Lunar Libration was Re: moon's synchronism




Lunar libration allows us to see about 59% of the lunar surface if we
observe the moon over a long enough period of time. It has two components.

The libration in latitude is due to the 5 deg. inclination of the moon's
orbit to the ecliptic. Sometimes we can look over the top of the lunar north
pole and sometimes up at the lunar south pole.

The libration in longitude is due to the eccentric lunar orbit and
consequent changing angular velocity. The lunar axial rotation is very
stable and when coupled to the changing orbital velocity allows us to see
around the leading edge of the moon.

Mathematica has a package available called "Scientific Astronomer"
which can produce a very good animation showing lunar libration. I have also
used it to produce graphs showing libration in latitude and longitude as a
function of time.

The animation will work using the Mathmatical "Math Reader" program which is
free and can be downloaded from www.wolfram.com . I will send the animation
and plots to anyone on the list interested.

Paul Middents
Olympic College
Bremerton, WA.