Quick background on the moons phase.
Search terms lunar, phase, diagram, moon.
See http://en.wikipedia.org/wiki/Lunar_phase for a good explanation of all things lunar.
Movement
- Waxing Moon moves from a New to a Full moon.
- Waning Moon moves from a Full to a New moon.
Phases
- New Moon is 100% Shadow, as it’s exactly between the earth and the sun.
- Waxing Crescent
- First quarter
- Waxing Gibbous
- Full Moon is 0% Shadow, as it’s behind the earth and completely illuminated by the sun (except when eclipsed by the earth).
- Waning Gibbous
- Last Quarter
- Waning Crescent
Orbital data
- Moon day equals 27.3 days.
- Orbits earth in 27.3 days (Sidereal month).
- Completes phases in 29.5 days (Synodic month).
Check http://en.wikipedia.org/wiki/Sidereal for more info on orbital periods.
Direction of the waxing and waning depends on which hemisphere you’re looking from. Though I’m confused as to what might happen at the equator. My guess is that the shadow should be rotated based on longditude.
This class represnts the moons phase as a percentage %.
0% to %50 describes Waxing moon.
50% to 100% describes Waning moon.
So 0% AND 100% both describe a New Moon in full shade and 50% describes a Full Moon fully lit.