Diogenes Laertius Vitae philosophorum 7.1.146

[146] For the moon is seen approaching at conjunctions and occulting it and then again receding from it. This can best be observed when they are mirrored in a basin of water. The moon is eclipsed when she falls into the earth’s shadow: for which reason it is only at the full moon that an eclipse happens [and not always then], although she is in opposition to the sun every month; because the moon moves in an oblique orbit, diverging in latitude relatively to the orbit of the sun, and she accordingly goes farther to the north or to the south. When, however, the moon’s motion in latitude has brought her into the sun’s path through the zodiac, and she thus comes diametrically opposite to the sun, there is an eclipse. Now the moon is in latitude right on the zodiac, ¹ when she is in the constellations of Cancer, Scorpio, Aries and Taurus: so Posidonius and his followers tell us.