Eclipse Glossary
- Annular Eclipse
-
The distance from the Earth to the Moon varies slightly since the Moon's orbit around
the earth is slightly elliptical (oval shaped). When the Moon is farther from the
Earth the disk of the Moon appears smaller. When closer, the disk appears larger.
During some eclipses, the Moon is relatively far away and the apparent size of the
Moon is correspondingly smaller. During these eclipses, the Moon appears too small
to completely cover the Sun and the eclipse is a kind of partial eclipse where a ring
of sunlight is visible around the edges of the moon. There are more annular eclipses
than total eclipses. This was not always the case as the Moon is slowly getting farther
from the Earth. Eventually, there will be no more total eclipses.
Eclipse photographs copyright 1999 by Fred Espenak, courtesy of www.MrEclipse.com
- Annular-Total Eclipse
-
An eclipse which starts as an annular eclipse, changes to a total eclipse along its
path on the Earth, and returns to an annular eclipse before the end of the eclipse
path.
- Baily's Beads
-
Seen just before or after totality, these are tiny bits
of sunlight passing through throught the valleys at the rim of the Moon.
- Eclipse Path
-
As the Moon orbits the Earth and the Earth rotates under the Moon, the shadow of the
Moon during an eclipse moves across the Earth. Thus, one eclipse can be seen in many
places on the Earth as the Moon's shadow moves. The path the shadow takes during an
eclipse is the eclipse path (movie).
- Partial Eclipse
-
A partial eclipse is one in which a portion of the Sun's surface is not covered by
the Moon.
- Penumbra
-
The penumbra is the portion of the Moon's shadow from which only a portion of the
Sun's light is blocked. If you are in the penumbra, you are seeing a partial eclipse.
- Saros Cycle
-
The geometry of the Sun, Moon, and Earth very nearly repeats itself every 18 years.
if you take the time of a solar eclipse and add 6585.32 days to it, you will have
a good forecast for the occurence of another very similar eclipse. The most significant
difference from one eclipse in a Saros cycle to the next is the location of
the eclipse on the Earth.
- Shadow Bands
-
Shadow bands are faint ripples of light that sometimes are seen on the ground shortly
before or after a totality. These bands are caused by sunlight passing through air
with slightly different densities. This causes the light to bend slightly as the air
acts like a lens. This is similar to the bands of light seen at the bottom of a swiming
pool during daylight.
- Total Eclipse
-
The distance from the Earth to the Moon varies slightly since the Moon's orbit around
the earth is slightly elliptical (oval shaped). When the Moon is farther from the
Earth the disk of the Moon appears smaller. When closer, the disk appears larger.
In a total eclipse , the Moon is close enough to the Earth so that the Moon's shadow
extends all the way to the surface of the Earth. for anyone in the shadow, the Sun
is completely blocked by the Moon and darkness descends briefly. A total eclipse is
one of the most awe-inspiring celestial events one can witness.
- Totality
-
The time during a total solar eclipse during which the Sun is completely covered by
the Moon.
- Umbra
-
The umbra is the central, dark portion of the Moon's shadow. If you are in the umbra,
you are seeing a total eclipse.
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