5f: Why do we observe annular solar eclipses seldom?
Keine Angabe
Fig. 44: The variable apparent diameter of Moon for different distances from the Earth

Rarely one can observe annular solar eclipses. The apparent size of the moon varies within narrow limits, because the moon is running on an elliptic orbit around Earth.
While the moon is close to the earth (Perigee, about 360.000 km from Earth), the apparent sizes of the sun and the moon are the same.
If the distance Earth - Moon is larger (Apogee, about 405.000 km from Earth), Moon appears to be smaller for us.


This condition, which can account for up to 14 % (see: Fig. 44), must prevail precisely when the moon passes a lunar node (Nodes are intersections of the moon's orbit plane with the ecliptic).
In this situation however, Moon does not quite cover the sun and you will get an annular eclipse.
The number of annular solar eclipses is so low because a large number of conditions must be met.


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