Umbra
The umbra is the dark inner core of a shadow, where the light source is blocked completely.
Full definition of Umbra →:: COMPARE ::
UmbravsAntumbra
The short answer
The antumbra begins where the umbra's cone tapers to a point and ends. Inside the umbra the Moon covers the Sun entirely, giving a total eclipse; inside the antumbra the Moon is too small to cover it, so a ring remains. Same geometry, one distance apart.
Side by side
| Aspect | Umbra | Antumbra |
|---|---|---|
| Sun is | Fully covered | Ringed |
| Eclipse type | Total | Annular |
| Position | Before the cone's tip | Beyond it |
| Moon appears | Larger than Sun | Smaller |
What each one means
Antumbra
The contrast above sets out how Antumbra differs from Umbra on the points that actually matter.