The Moon
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400 BC meton
27 1/3 days - 27d 7h43m11.5s
Synodical Month 29.5
The Moon travels east with respect to the stars, meaning that it rises later
each night. The time lapse between moon rise on
successive nights is known as the
retardation.
This retardation can be of the order of an hour, although the Harvest Moon in September only
rises about 15 minutes later each evening. This variation is due to the
inclination of the Moon's path to the ecliptic.
Because of elliptical orbit, a libration of longitude allows our perspective to vary
by 7°.
Because of the Moon's imclination to ecliptic of 5° and
its spin axis is 1.5° to this, a libration of latitude of up
to 6.5° occurs.
Diurnal libration occurs because the Earth is not a point but an extended body. An observer
on the Earth can see up to about 1° extra around the edge.
Altogether we are able to view 59% of the surface at one time or another.
During an eclipse the moon will be full.
The maximum number of solar and lunar eclipses possible in one year is 7.
Eclipse can only occur at the nodes
These nodes move slowly westwards (regression of the nodes) because of the Sun's
gravitational pull.
When a lunar eclipse is seen it is visible from a complete hemisphere of the Earth
(unlike a solar eclipse). It can be either a total eclipse, when the Moon is in the
Earth's umbra, or a partial eclipse, when the Moon is in the Earth's penumbra
(which is not too easy to detect).
Totality can last for up to 1 hour 44 minutes.
By virtue of the bending of some sunlight thru the Earth's atmosphere, the Moon is always
visible during a lunar eclipse. The color is often described as 'coppery' - the exact nature
varies from one eclipse to the other.
Eclipses were used by the ancient Greeks to deduce that the Earth was a sphere.
This was mentioned by Aristotle (around 300s BC).
(by 200BC, they had a fairly accurate measure of the size of this sphere, see Eratosthenes).
moon worst view at full moon. Seem best near the terminator when the floor is
filled with shadow, either
fully or partially.
Copernicus
Tycho
Bombardment by heavy object
terminator
mass 1.2% that of Earth's
The map is 'the wrong way up' showing the view which
would be seen in a telescope.
Data
Phases
Earth has opposite phases
Sidereal Month and Synodic Month
The Sidereal Month, i.e. with respect to the stars is
Libration
Lunar Eclipse
Craters
Mascons
Moon showing Apollo Landing Sites
