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diff --git a/doc/kstars/csphere.docbook b/doc/kstars/csphere.docbook new file mode 100644 index 00000000..913463ff --- /dev/null +++ b/doc/kstars/csphere.docbook @@ -0,0 +1,28 @@ +<sect1 id="ai-csphere"> +<sect1info> +<author> +<firstname>Jason</firstname> +<surname>Harris</surname> +</author> +</sect1info> +<title>The Celestial Sphere</title> +<indexterm><primary>Celestial Sphere</primary> +<seealso>Celestial Coordinate Systems</seealso> +</indexterm> +<para> +The celestial sphere is an imaginary sphere of gigantic radius, centered +on the Earth. All objects which can be seen in the sky can be thought +of as lying on the surface of this sphere. +</para><para> +Of course, we know that the objects in the sky are not on the surface of +a sphere centered on the Earth, so why bother with such a construct? +Everything we see in the sky is so very far away, that their distances +are impossible to gauge just by looking at them. Since their distances +are indeterminate, you only need to know the <emphasis>direction</emphasis> +toward the object to locate it in the sky. In this sense, the celestial sphere +model is a very practical model for mapping the sky. +</para><para> +The directions toward various objects in the sky can be quantified by +constructing a <link linkend="ai-skycoords">Celestial Coordinate System</link>. +</para> +</sect1> |