《Tetrabiblos》The Zodiacal PlanisphereClaudius Ptolemy（Ashmand 英譯 1822）
In his first example, Ptolemy directs 0° ♉ to be placed on the ascendant, so that the beginning of ♑ may be on the mid-heaven; 0° ♊ must, therefore, fall on the point A, distant from the mid-heaven 147° 44′ of the equator, as measured by the line AB; because every point in the sphere always preserves one and the same parallel with the equator; and 0° ♊, in passing to the mid-heaven, must proceed along the line AB.
段落 tetra-4-thezodiaca-7public-domain (Ashmand 1822)
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