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2. TECHNICAL TERMS
For an interesting reading, it is desirable to acquaint the readers with certain terms used in astronomy at present, so that the ancient material could be brought under relevance.
Z
CELESTIAL DIAGRAM
The above is a celestial diagram used in spherical trigonometry and astronomy. An observer is set at O inside a hollow sphere, serving as two hemispherical domes, with Z as the Zenith and Z' as the nadir. This is presumed to be his range of vision in which all the heavenly bodies appear in different positions, measured through various types of celestial coordinates. S N is his horizon, with East (E), West (W), North (N), South (S) as its
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