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Geolens

Case study US

Full Moon, Yosemite

Yosemite Valley

Seeing a full Moon above Yosemite’s cliffs depends on lunar phase, its path across the sky and the observer’s viewpoint. An eclipse requires an additional alignment.

Nearly full Moon photographed from Hamois, Belgium, with dark maria and bright cratered highlands.
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Nearly full Moon photographed from Hamois, Belgium. The phase is nearly the same for observers in Wales and California at the same instant; local rise times and the disc's orientation differ.
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Location: 37.74°, -119.57°

At full Moon, the Moon is approximately opposite the Sun as seen from Earth. A mountain can delay its appearance above the visible horizon, so landscape photographs depend on both astronomical geometry and the local line of sight.

Most full Moons pass above or below Earth’s shadow because the lunar orbit is inclined. Use the eclipse model to locate an orbital node and explain why a full Moon alone is not enough for a lunar eclipse.

Open this state in the lab

Exam-style question

Why is a full Moon necessary but not sufficient for a lunar eclipse?

Teacher hint: A lunar eclipse needs a full Moon close enough to an orbital node for it to pass through Earth’s shadow.

Process labs

EclipsesMoon phases and Sun–Earth–Moon geometry

Sources

  • NASA / NPS