@cikljamas start thinking 3D.
The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space.[1] As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane.
Celestial equator - Wikipedia, the free encyclopedia
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/61/AxialTiltObliquity.png/391px-AxialTiltObliquity.png)
Celestial sphere - Wikipedia, the free encyclopedia
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Earth_within_celestial_sphere.gif/200px-Earth_within_celestial_sphere.gif)
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with a particular celestial body. All objects in the observer's sky can be thought of as projected upon the inside surface of the celestial sphere, as if it were the underside of a dome or a hemispherical screen. The celestial sphere is a practical tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant.
![](http://upload.wikimedia.org/wikipedia/commons/5/58/Earth_tilt_animation.gif)
The axis of a planet remains oriented in the same direction with reference to the background stars regardless of where it is in its orbit. Northern hemisphere summer occurs at the right side of this diagram, where the north pole (red) is directed toward the Sun, winter at the left.
Axial tilt - Wikipedia, the free encyclopedia
Al
The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space.[1] As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane.
Celestial equator - Wikipedia, the free encyclopedia
![](http://upload.wikimedia.org/wikipedia/commons/thumb/6/61/AxialTiltObliquity.png/391px-AxialTiltObliquity.png)
Celestial sphere - Wikipedia, the free encyclopedia
![](http://upload.wikimedia.org/wikipedia/commons/thumb/1/12/Earth_within_celestial_sphere.gif/200px-Earth_within_celestial_sphere.gif)
In astronomy and navigation, the celestial sphere is an imaginary sphere of arbitrarily large radius, concentric with a particular celestial body. All objects in the observer's sky can be thought of as projected upon the inside surface of the celestial sphere, as if it were the underside of a dome or a hemispherical screen. The celestial sphere is a practical tool for spherical astronomy, allowing observers to plot positions of objects in the sky when their distances are unknown or unimportant.
![](http://upload.wikimedia.org/wikipedia/commons/5/58/Earth_tilt_animation.gif)
The axis of a planet remains oriented in the same direction with reference to the background stars regardless of where it is in its orbit. Northern hemisphere summer occurs at the right side of this diagram, where the north pole (red) is directed toward the Sun, winter at the left.
Axial tilt - Wikipedia, the free encyclopedia
Al
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