They're both imaginary, and they're parallel.
How to explain their relationship . . .
Imagine the earth's equator ... the circular line drawn around the earth's fat middle, exactly half-way
between the North and South Poles. Now imagine that the equator starts to get bigger. It's still lined up
with the same line on the earth, but its diameter is growing, and it loses contact with the surface, and keeps
growing, until it's over everybody's head. Now ships are sailing under it on their way north or south, and
it still keeps growing, like an enormous hula hoop (does anybody still know what those are?).
After a few hours, the equator gets so big that we can't really tell any more that it's only a few hundred miles
out there. Now it looks like it's a line on the solid surface of the sky ... the same surface that the sun, moon,
and stars are all painted on. Everything drawn on that surface looks like it's the same distance above the
earth ... the surface looks like the inside of a big globe. And it has that new line all the way around it, exactly
above the earth's equator at every point, but up in the sky. That's the celestial equator.
Another way to visualize the celestial equator ... maybe not a lot better than the first way, but here it is anyway:
Picture a gigantic knife, big enough to come along and cut the whole earth in half.
If it's big enough and comes in exactly right, it can cut the earth exactly on the equator, so you separate the bottom
half from the top half. Those are the north and south "hemispheres". Now, each half of the earth can sit flat on a table,
and the outside of the circle that it makes on the table is the line that used to be the equator.
OK ? Good.
Now if you will, picture an even BIGGER knife, one that makes the first one look like a boy scout's pocket knife.
This one is truly ginormous, almost too big to imagine. It can slice stars, solar systems, galaxies ! We're going to
slice the earth in half again with this one, and it has to be a clean cut. So we back way off almost to infinity, and
carefully line up our shot, so that we won't have to make any adjustments on the way in. When we're perfectly
lined up, we make our move. We keep our knife flat, come in smooth and steady from infinity, hit the equator
exactly, and slice precisely between the hemispheres. Then we follow through, and keep going off to infinity
on the other side, holding the knife flat all the way.
We have not only cut the earth in half exactly along the equator. This time we have also cut the whole
celestial sphere in half, on a line exactly parallel to the earth's equator. That line is (was) the celestial equator.
These are imaginary locations in the sky. The "celestial sphere" is a blanket term for everything beyond the Earth. The celestial equator is the plane of the Earth's equator extended out into space. The "celestial poles" are extensions of the north pole and south pole into space. It's sometimes convenient to describe objects out in space with reference to terrestrial coordinates.
Celestial Equator
No, the celestial equator does not always pass directly overhead. The position of the celestial equator in the sky is determined by the observer's latitude on Earth. If the observer is located at the equator, the celestial equator will pass directly overhead. However, for observers at different latitudes, the celestial equator will appear at an angle to the horizon.
The altitude at which the celestial equator intersects your local meridian is the complementof your latitude, i.e. the difference between your latitude and 90 degrees.On the equator: Your latitude is zero. (90 - 0) = 90. Celestial equator passes overhead.At the pole: Your latitude is 90. (90 - 90) = 0. Celestial equator coincides with the horizon.In New Orleans, Louisiana, or Durban, South Africa: Your latitude is 30. (90 - 30) = 60.Celestial equator intersects local meridian at 60 degrees above the horizon.
The celestial equator is the imaginary line in the heavens that runs around the Earth midway between the celestial poles. It is an extension of Earth's equator onto the celestial sphere and divides the sky into northern and southern hemispheres.
These are imaginary locations in the sky. The "celestial sphere" is a blanket term for everything beyond the Earth. The celestial equator is the plane of the Earth's equator extended out into space. The "celestial poles" are extensions of the north pole and south pole into space. It's sometimes convenient to describe objects out in space with reference to terrestrial coordinates.
celestial equator
Celestial Equator
No, the celestial equator does not always pass directly overhead. The position of the celestial equator in the sky is determined by the observer's latitude on Earth. If the observer is located at the equator, the celestial equator will pass directly overhead. However, for observers at different latitudes, the celestial equator will appear at an angle to the horizon.
The celestial equator passes through 15 major constellations, including 5 from the Zodiac:AquilaAquariusCanus MinorCetusEridanusHydraLeoMonocerosOrionOphiuchusPiscesSerpansSextansTaurusVirgo
If Earth did not rotate, the celestial poles would align with the geographic poles, and the celestial equator would align with Earth's equator. The celestial poles are points in the sky that the Earth's axis points towards, and the celestial equator is an imaginary line in the sky directly above the Earth's equator. Without Earth's rotation, these references would be fixed in the sky.
The altitude at which the celestial equator intersects your local meridian is the complementof your latitude, i.e. the difference between your latitude and 90 degrees.On the equator: Your latitude is zero. (90 - 0) = 90. Celestial equator passes overhead.At the pole: Your latitude is 90. (90 - 90) = 0. Celestial equator coincides with the horizon.In New Orleans, Louisiana, or Durban, South Africa: Your latitude is 30. (90 - 30) = 60.Celestial equator intersects local meridian at 60 degrees above the horizon.
Half. The other half is south of the celestial equator.It depends on the where you're looking from (at the equator it is half and half). If you are at latitude 30 degrees north, then about 2/3 of "your" sky is north of the celestial equator (30 degrees north means that you are one-third of the way north from the equator to the North Pole.)
The celestial equator is the imaginary line in the heavens that runs around the Earth midway between the celestial poles. It is an extension of Earth's equator onto the celestial sphere and divides the sky into northern and southern hemispheres.
A declination of +30 degrees. This means it is 30 degrees north of the celestial equator.
The angle between the celestial equator and your personal zenith is equal to the latitude of your location. (Whether it's north or south latitude doesn't matter, and neither does your longitude or the time of day or night where you are.)
On Friday, October 21, 2005 the moon was located South of the celestial equator.