Making Sun, Moon and Earth line up.
Why isn’t there an eclipse every month?
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Why isn’t there an eclipse every month?
Line up phase and node before tracing the shadow.
New Moon geometry can produce a solar eclipse and full Moon geometry can produce a lunar eclipse. But the Moon’s orbit is tilted: the bodies must also align near an orbital node so the shadow actually reaches its target.
Schematic scale. Moon orbital latitude β≈tilt×sin(angle−node). Eclipse tolerance 0.5° is an illustrative alignment gate, not a real eclipse forecast. Solar near new Moon; lunar near full Moon.
Make a solar eclipse at new Moon or a lunar eclipse at full Moon.
Align the Moon’s phase and orbital node for an eclipse.