- A great circle is
a circle that divides
sphere into equal
halves.
(i.e., in twain).
- A small circle
a circle that divides a
sphere unequally.

Caption: The basic idea of the celestial sphere.

A basic point for the discussion of the celestial sphere:

Image link: Itself.

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File: Celestial sphere file: celestial_sphere_000_basic_idea.html.