As we continue reading through al-‘Awwā’, Ibn Mājid tells us about the positions of the lunar mansions in the solar zodiac. “At the time of Alexander,” the first northern and southern mansions were al-Sharatān and al-Ghafr respectively—what this means is that, around the fourth century BC, al-Sharatān was the first mansion to be seen rising after the vernal equinox; and Al-Ghafr the first after the autumn equinox—“but they are different in our time, in respect to the zodiac.”
Unlike the mansions of the moon, which correspond to stars visible in the night sky, the solar zodiac was determined by the tropical year. The Babylonian system inherited by the Greeks divided the zodiac into twelve equal divisions of 30 degrees, starting near αβ Arietis, on which the equinoctial sun rose around the year 400 BC.
Nowadays, the zodiac is divided in the same way: the sun is said to be in Aries after the vernal equinox, to be in Taurus after 30 degrees, in Gemini after 60, and so on. However, due to the Earth’s axis movement (the precession movement), the equinoctial points have been slowly shifting to the west in relation to the stars in the background. Even though Aries conventionally begins after the spring equinox, the constellation actually seen rising at that period is Pisces. At the time of Ibn Mājid, “when the sun or the moon descend in al-Sharatān (αβ Arietis), only six degrees of Aries remain there, and all of al-Butayn (εδρ Arietis) is within Taurus.” The lunar zodiac remained throughout a sidereal system, and this is one of the reasons why it had, and still may have, very practical usages for navigation. [IB]
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