Tuesday, April 15, 2014

Lunar eclipse: April 14, 2014

Moon--lunar eclipse
Moon, eclipse just starting. April 14, 2014. Greg Gillson .
I stayed up late last night to watch the eclipse.

Moon--lunar eclipse
The Earth's shadow creeps across the moon.
These photos were hand-held, held against the porch railing, with my Canon XTi and 100-400mm IS lens--my bird photography setup.

Moon--lunar eclipse
Moon nearly completely in the Earth's shadow.
So, I was thinking, why isn't there a lunar eclipse every time there was a full moon during spring and fall equinox--when the days and nights are equal and the earth's poles are perpendicular to its orbit around the sun. Obviously, there aren't eclipses always and only then. One reason, it turns out, is that the moon is 5% outside the equatorial path. Another is that the moon's gravity slows the rotation of the earth in a complex way. So it's not straightforward to predict eclipses, especially to determine how much of the earth's shadow falls on the moon.
Moon fully in shadow of the Earth.