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"The solstices and the equinoxes define the colures of declination and of ascension that intersect under the poles of the earth along the axis of the heavens at spherical right angles. But the equinoctial colures that lie along the zodiac make oblique angles and make right angles along the zodiac of the solstices." (Cosmographiae introductio, chap. IV - Hessler 2008)