Posted by Art on October 23, 1997 at 08:11:51:
In Reply to: Meridian posted by Gloria Su on October 21, 1997 at 19:29:08:
: I know David Choi asked a question already about the meridian, but I'm still somewhat confused. Just to clarify: Is the meridian basically like the equator that runs north and south instead? Does it go full circle around the celestial sphere? Is this the line that goes through the vernal equinox (which we use to measure right ascension)? Can you also explain that--about the meridian and the vernal equinox? If the meridian is a line, does it also run through the autumnal equinox? Thanks for taking time to answer my questions. I really appreciate it.
:
The meridian is an imaginary line that runs from the north point on the horizon, up near Polaris, up through zenith, and down to the south point on the horizon.
It is local to your position on Earth; each location has its own meridian.
It has nothing directly to do with the equinoxes.
Nominally, it circles the celestial sphere, but we would probably think of the part below the horizon as the anti-meridian.
Every celestial object reaches its highest point in the sky when it crosses the meridian.
Local noon is the time the Sun crosses the meridian.
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