equinox question

Today was the vernal equinox.
According to my understanding, this is a day on which the sun rises
and sets approximately due east and west and takes approximately 12
hours to make that trip. But Starry Night pro and a couple other
databases tell me that Sol rose at approx. 05:55 and set at approx.
18:04. The closest to a 12-hour day was on March 16.
My intuitive sense of this is that latitude should not be a factor. Am
I wrong in that assumption?
What am i missing?

--
unDO email address
___
Nature, heron stone
to be commanded,
must be obeyed. http://home.comcast.net/~heronstone/

Heron stone posted:

Today was the vernal equinox.
According to my understanding, this is a day on which the sun rises
and sets approximately due east and west and takes approximately 12
hours to make that trip. But Starry Night pro and a couple other
databases tell me that Sol rose at approx. 05:55 and set at approx.
18:04. The closest to a 12-hour day was on March 16.
My intuitive sense of this is that latitude should not be a factor. Am
I wrong in that assumption?
What am i missing?

The vernal equinox occurs when the center of the sun's disk is directly over a
point on the sky where the ecliptic (the plane of the Earth's orbit) and the
plane of the Celestial equator cross (the point is called "the first point of
Aries (actually is located in Pisces). The sun, from our vantage point,
appears to be "moving" into the northern half of the celestial sphere, so the
vernal equinox is generally indicated as the time when spring begins in the
northern hemisphere. The date for equal times of sunrise and sunset differ
slightly from the date of the equinoxes, as the sun appears to be moving
constantly against the star background as the day goes on. This apparent
motion (along with the fact that the path the sun takes is tilted) is enough
that it will tend to cause the "equal day/night" date to be a bit different
from the exact date for the equinox. Clear skies to you.
--
David W. Knisely
Prairie Astronomy Club: http://www.prairieastronomyclub.org
Hyde Memorial Observatory: http://www.hydeobservatory.info/

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