In fact, he excuses himself for this in the twelfth book of the Metaphysics, where he clearly proves himself to have followed also another opinion where he was obliged to speak of Astrology.

Ptolemy, then, perceiving that the eighth sphere is moved by many movements, seeing its circle to depart from the right circle, which turns from East to West, constrained by the principles of Philosophy, which of necessity desires a Primum Mobile, a most simple one, supposed another Heaven to be outside the Heaven of the fixed stars, which might make that revolution from East to West which I say is completed in twenty-four hours nearly, that is, in twenty-three hours, fourteen parts of the fifteen of another, counting roughly.
Therefore, according to him, and according to that which is held in Astrology and in Philosophy since those movements were seen, there are nine moveable Heavens; the site of which is evident and determined, according to an Art which is termed Perspective, Arithmetical and Geometrical, by which and by other sensible experiences it is visibly and reasonably seen, as in the eclipses of the Sun it appears sensibly, that the Moon is below the Sun; and as by the testimony of Aristotle, who saw with his own eyes, according to what he says in the second book on Heaven and the World, the Moon, being new, to enter below Mars, on the side not shining, and Mars to remain concealed so long that he re-appeared on the other bright side of the Moon, which was towards the West..