Lunar Eclipse Geometry
Interactive simulation — adjust parameters and watch the visualization update in real time.
How it works
A lunar eclipse happens at full Moon when the Moon enters Earth’s shadow. The umbra is where the Sun is completely hidden by Earth; the penumbra receives only part of the sunlight. The Moon’s orbit is tilted, so not every full Moon is eclipsed.
Key equations
Same tangent construction as solar eclipses, but Earth is the occluder and the Moon is in the shadow cone.